UNIVERSITY OF PARDUBICE FACULTY OF CHEMICAL TECHNOLOGY

DEPARTMENT OF GENERAL AND INORGANIC CHEMISTRY

EXPERIMENTAL AND THEORETICAL

STUDY OF HYPERFINE COUPLING

OF VANADOCENE COMPLEXES

Annotation of the PhD Degree Thesis

AUTHOR: Ing. Jan Honzíček SUPERVISOR: Doc. Petr Nachtigall, PhD.

2005

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The PhD degree Thesis was carried out at Department of General and

Inorganic Chemistry of University of Pardubice in years 2002-2005.

Candidate: Ing. Jan Honzíček

Reviewers:

The PhD Thesis will be defended at University of Pardubice in face of

Commission for Defending Doctoral Thesis chaired by............................

on.............................. 2005.

The PhD Thesis will by available to those interested in the central library

of University of Pardubice.

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1. Introduction

Metallocene complexes of the type Cp2MX2 (M = early transition metal; X - halide,

pseudohalide) are currently largely investigated due to their biological [1, 2] and catalytic

activity [3, 4]. Currently known studies show that such activity is closely connected with

the metallocene complex structure [5, 6].

X-ray structure analysis and spectroscopic methods are useful for the structure

investigation. X-ray analysis can be used only for single crystals of the compounds. The

isolation of the compounds in the solid state and preparation of the single crystal is

sometimes very is difficult or impossible. Therefore spectral methods are often used for

structure investigation.

NMR spectroscopy cannot be used for paramagnetic compounds therefore the

interpretation of vibration spectra are in point of the interest. Infrared and Raman spectra

give important information about the structure of the metallocene complexes. Based on

such methods it is possible to find out the presence of the metallocene fragment with two

η5-bonded cyclopentadienyl rings [7].

This work is attended especially for the study of vanadocene complexes by EPR

spectroscopy. The presence of the magnetic active nucleus (51V, I = 7/2, 99,8 %) causes the

hyperfine coupling (HFC) that is very sensitive to changes in the coordination sphere of the

central metal. Some problems occurs with the assignment of the obtained EPR parameters

to the concrete species, when the particular structure is not known from another

experimental technique. Such problems can be solved by theoretical calculations. Recently,

EPR parameters of some 3d-metal compounds were theoretically investigated at the DFT

level of the theory [8-12].

- 3 -

2. Results and Discussion

2.1 Synthesis and Vanadocene Complexes

Metallocene complexes of the type Cp2VX2 and Cp'2VX2 (X = NCO, NCS, N3, CN,

dca, tcm, dcnm; Cp = η5-C5H5, Cp' = η5-CH3C5H4, Scheme 1), were prepared by reaction

of vanadocene dichloride with the large excess of the sodium or potassium salt of the

corresponding pseudohalide.

2a: R = H X = NCO3a: R = H X = NCS4a: R = H X = N35a: R = H X = CN6a: R = H X = dca7a: R = H X = tcm8a: R = H X = dcnm

NaX+ + NaCl(KX) (KCl)V XX

R

R

V ClCl

R

R

1a: R = H 1b: R = CH3

2b: R = CH3 X = NCO3b: R = CH3 X = NCS4b: R = CH3 X = N35b: R = CH3 X = CN6b: R = CH3 X = dca7b: R = CH3 X = tcm8b: R = CH3 X = dcnm

Scheme 1 Synthesis of pseudohalide complexes.

Monosubstituted derivatives (Cp2VClX) are formed by ligand-exchange reaction. The

EPR spectra measurements show that all prepared complexes are contaminated with

disubstituted compounds (Scheme 2). Only complex Cp2VCl(tcm) (7c) was successfully

separated from complex 7a by extraction, because these complexes show very different

solubility in organic solvents.

Na(tcm)+ + NaClV ClCl V tcm

tcm+V Cltcm

1a 7c 7a

Scheme 2 Reaction of complex 1a with Na(tcm).

- 4 -

Complexes of carboxylic acids Cp2VX2 a Cp'2VX2 (X = OOCH, OOCCCl3, OOCCF3;

X2 = (OOC)2, (OOC)2CH2; Cp = η5-C5H5, Cp' = η5-CH3C5H4; Scheme 3), were prepared

by reaction of vanadocene dichloride with corresponding carboxylic acid.

RCOOH+ HCl

1a: R = H 1b: R = CH3

V ClCl

R

R

O

OR

VO

OR

R

R

9a: R1 = H R2 = H10a: R1 = H R2 = CCl311a: R1 = H R2 = CF3

9b: R1 = CH3 R2 = H10b: R1 = CH3 R2 = CCl311b: R1 = CH3 R2 = CF3

1

11

1

2

2

A COOHHOOC

R

OO

VO

O

A

1

1

R

12b: R1 = CH3 A = 13b: R1 = CH3 A = CH2

12a: R1 = H A = 13a: R1 = H A = CH2

Scheme 3 Synthesis of carboxylic acid complexes

2.2 X-ray structures

The structures of the complexes Cp'2V(NCO)2 (2b), Cp2V(NCS)2 (3a), Cp2V(N3)2 (4a),

Cp2V(dca)2 (6a), Cp'2V(dca)2 (6b), Cp2VCl(tcm) (7c), Cp'2V(dcnm)2 (8a),

Cp2V(OOCCCl3)2 (10a), Cp'2V(OOCCF3)2 (11b) and Cp2V(OOC)2 · 0.5(COOH)2 (12a)

were determined by X-ray diffraction analyses.

Complexes have typical bent metallocene structure with two η5-bonded Cp (Cp') rings

and two donor atoms of other ligands around the vanadium(IV) center. The substitution of

chloride ligands does not change the geometric parameters of the vanadocene moiety (Cg-

V 1.95-1.98 Å, Cg-V-Cg 133-136°).

1,1'-dimethyl substituted complexes show different location of methyl groups. Complex

Cp'2V(NCO)2 (2b) has one methyl group bellow the X–V–X moiety and the second one at

the side (Fig. 1a). Complexes Cp'2V(dca)2 (6b) and Cp'2V(dcnm)2 (8b) have methyl groups

above and bellow the X–V–X moiety (See Figs. 2b and 3b, respectively). The methyl

groups of the compound Cp'2V(OOCCF3)2 (11b) are positioned at the opposite sides of the

molecule, directed away from each other (Fig. 4b).

- 5 -

a) b)

N1

C9C8

C7

C3

C2C1

C5C4

V1

C10

C6S2 C12

N2

S1 C11

C25

C24

C23C22

C21

C15

C11

C14

C13

C12

C26

C16

N1 C1O1

O2C2N2

V1

c)

N1

C5C3

C2C1

C6

C10

C9

C7

C8

V1

N6

N5

N4

N3

N2

Fig. 1 X-ray structure of the complexes: a) Cp'2V(NCO)2 (2b); b) Cp2V(NCS)2 (3a); c) Cp2V(N3)2 (4a).

The results of X-ray structure analyses show that pseudohalide ligands are bonded via

nitrogen atom to the vanadocene moiety in compounds 2a, 3a a 4a (Fig. 1). The bond

distances V–N were found in narrow range from 2.03 to 2.08 Å.

Complexes Cp2V(dca)2 (6a) and Cp'2V(dca)2 (6a) have both bent dca ligands bonded

via terminal nitrogen atom (V–N = 2.04 - 2.05 Å). The geometry of dca ligands are

affected by coordination to vanadium(IV). Although the coordinated and non-coordinated

C≡N bond lengths is the same (1.145(3) - 1.157(2) Å), the N–C bonds beside coordinated

cyano-groups are significantly shorter ([1.286(3) - 1.301(3) Å] than beside non-

coordinated groups [1.308(3)-1.322(3) Å]. Such distortions can be explained by two

possible resonance structures, see Scheme 4.

- 6 -

a) b)

N1

N5

N3 C2

C4

N6C7

N8

C9

N10

V1

C25C24

C21C23

C22

C11C12

C13

C14

C15

N10

C9

N8

C2

C7

C26C21

C22C23

C24

C25

C11

C16C15C14

C13C12

N6

N1

V1 N5C4

N3

Fig. 2 X-ray structures of the complexes: a) Cp2V(dca)2 (6a); b) Cp'2V(dca)2 (6b).

N

N

NO

O-

N

N

NO

O-

N

N

N

O- N

N

N

O-

NN

N

O-NN

N

O-

Scheme 4 Resonance structures of non-linear pseudohalides.

The unit cell of the compound Cp2VCl(tcm) 7c consists of four crystallographically

independent but essentially the same molecules. One of them is shown in the Figure 3a.

The planar tcm ligand is bonded to the vanadocene moiety through the nitrogen atom. The

bond distances V–N (2.054(3) - 2.071(4) Å) are comparable with dca compounds 6a and

6b.

The geometry of planar tcm ligand shows significant distortions that can be explained in

similar way as for dca complexes. Two possible resonance structures are depicted in

Scheme 4. The contribution of second resonance structure causes significant contraction of

C-C bonds that are beside coordinated cyano-groups (C-C = (1.387(6) - 1.400(6) Å). The

C-C bond that are positioned beside non-coordinated cyano-groups were found in the range

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from 1.399(8) to 1.1414(6) Å. The bond distances of the cyano-groups are not affected by

coordination (C≡N = 1.144(6) to 1.159(5) Å).

a) b)

C4C5

C1C6

C2

C3

O1a

N3C9

N2

C8

C7

N1

O1V1

C47

C48 C49

C410

C46

C43

C414

N42

C413

C412C411N41

C45

C44C43 C42

C41Cl4

V4

Fig. 3 X-ray stuctures of the complexes: a) Cp2VCl(tcm) (7c); b) Cp'2V(dcnm)2 (8b).

Complex Cp'2V(dcnm)2 (8b) have two planar dcnm ligands bonded via oxygen atoms of

nitroso groups to the Cp'2V moiety (V–O = 2.035(1) Å, O–V–O = 74.78(5)°). The dcnm

ligands were found in one plane with vanadium atom (Pldcnm-PlO1VO1a = 4.81(5)°).

a) b) C4

C3

C2

C5

C1

V1

O2C6

O1

C7

Cl2

Cl1

Cl3

O1'

O1'

F3A

F2AF1A

C8

C7

O2

O1

C6

C5

C4C3

C2

C1

V1

Fig. 4 X-ray structure of the complexes: a) Cp2V(OOCCCl3)2 (10a); b) Cp'2V(OOCCF3)2 (11b).

Complexes 10a and 11b have two monodentate carboxylic acids bonded to the

vanadocene moiety (V–O1 ~ 2.03 Å; V···O2 ~ 3.5 Å). The bond lengths C–O (~ 1.26 Å)

and C=O (~ 1.21 Å) of the coordinated carboxylic acid correspond with the monodentate

bonding mode.

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Complexes 10a and 11b show different values of the O–V–O bond angle (10a: 77.6°;

11b: 89.7°). This one is evidently caused with different conformation of carboxylic acids.

Unlike the complex 10a, in which the carbonyl oxygens of the coordinated COO group

are pointed apart, in the case of the compound 11b these oxygens are pointed towards the

O–V–O angle (Fig. 4). Such differences manifests in different dihedral angles O1'–V–O1–C

(10a: 179.7°; 11b: 38.2°).

Complex of the oxalic acid (12a) forms a chelate. The bond distances V–O (2.02 Å) and

bond angle O–V–O (78.6°) are very similar to values found for complex 10a. The

compound 12a is a dimer in the solid state with two molecules of the complex connected

via oxalic acid bridge (Fig. 5).

C7C8

C9

C10

C6

V1

C3

C2

C1

C4

C5

O1

O2

C11O3

C12O4

O6

C13

O5

Fig. 5 X-ray structure of complex Cp2V(OOC)2 · 0,5 (COOH)2 (12a). The second part

of solvate is related by center of symmetry. Hydrogen bond is drawn as dashed

line (O6···O4 2.586(1)Å, O6-H6A···O4 178(2)°).

2.3 EPR spectra

The EPR spectra were measured for prepared complexes (2-13). The majority of the

pseudohalide complexes (2-4, 6-8) show similar values of the parameters |Aiso| a giso (see

Tab. 1). Only cyanide complexes 5a and 5b give the |Aiso| values much lower and giso

higher than the other vanadocene complexes. This one is caused by strong electron

withdrawing effect of the cyanide ligands. The decreased value of the |Aiso| constant is

caused by larger delocalization of the unpaired electron on the pseudohalide ligands.

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Table 1 EPR parameters of the pseudohalide complexes.

|Aiso| [MHz] giso |Aiso| [MHz] giso 2a 212.2 1.9818 2b 212.5 1.9820 3a 205.3 1.9844 3b 205.3 1.9844 4a 199.7 1.9827 4b 198.9 1.9804 5a 169.8 1.9948 5b 169.0 1.9944 6a 210.5 1.9844 6b 211.3 1.9841 7a 206.3 1.9840 7b 207.6 1.9845 7c 206.5 1.9836 8a 209.3 1.9810 8b 208.1 1.9817

Complexes of monocarboxylic acids 9-11 show very similar EPR parameters (|Aiso| ~

220 MHz, giso ~ 1.98, |Ax| ~ 240 MHz, gx ~ 1.99, |Ay| = ~ 360 MHz, gy ~ 1.95, |Az| ~ 60

MHz, gy ~ 2.00). It is evident that substitution of on monocarboxylic acid does not affect

either A-tensor or g-tensor.

Dicarboxylic acids complexes, presumable chelates, show some differences in A-tensor.

The parameters |Aiso| and |Ay| are much lower than were found for monocarboxylic acid

complexes. The values of these parameters increase with increased number of chelate ring

members.

Table 2 EPR parameters of carboxylic acid complexes.

|Aiso| [MHz] giso

|Ax| [MHz]

|Ay| [MHz]

|Az| [MHz] gx gy gz

9a 220.3 1.981 236.5 368.8 55.7 1.988 1.956 2.000 9b 220.8 1.981 245.2 358.7 58.5 1.986 1.952 2.006 10a 221.1 1.981 237.2 366.3 59.9 1.987 1.956 2.005 10b 222.2 1.980 249.0 356.2 61.4 1.988 1.952 2.001 11a 222.2 1.981 241.7 367.2 57.8 1.987 1.953 2.003 11b 222.5 1.981 250.3 357.3 59.9 1.985 1.952 2.007 12a 189.8 1.984 241.8 307.1 20.4 1.995 1.961 1.997 12b 190.8 1.984 240.5 308.7 23.2 1.990 1.963 1.999 13a 208.1 1.981 255.0 334.1 35.0 1.984 1.959 2.001 13b 207.6 1.981 248.2 335.2 39.7 1.984 1.957 2.003

Bis(cyclopentadienyl)vanadium(IV) complexes (series a) and their 1,1' dimethyl

substituted counterparts (series b) show very similar values of both A-tensor and g-tensor.

So, such substitution does not significantly affect the EPR parameters.

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2.4 Calculations of HFC tensor

EPR spectroscopy is the efficient method for experimental study of d1-vanadocene

compounds. The main problem of this method is the assignment of the hyperfine coupling

tensor (HFC) to a particular structure of the complex when the structure is not known from

the other experimental techniques. These reasons make for theoretical calculations of HFC

tensor.

The complexes of bio-ligands with nitrogen and oxygen donor atom (such as nucleic

acids, amino acids etc.) play important role in the research of the biological activity of the

transition metal complexes. Particularly, neutral and cationic complexes with such donor

atoms were included into this study.

15 OAO=acac16 OAO=hfpd17 OAO=trop18 NAN=bpy19 NAN=phen20 OAN=gly21 OAN=ala22 OAN=val

2+15 - 17

+

VO

OA

14

VBr

Br

VN

NA

18, 19

+

20 - 22

VO

NA

2.4.1 HFC tensor of vanadocene dichloride

Within the first order approximation the Aiso is determined by the contribution from

singly occupied MO (SOMO) and by the spin polarization of other orbitals, the core s

orbitals on vanadium in particular. It is now well understood that the various exchange-

correlation functionals give rather different values of Aiso [8]. The calculations on

vanadocene dichloride (1a) employing various exchange-correlation functionals

(summarized in Table 3) show very similar trends as observed for other transition metal

compounds [8, 12].

With increasing amount of exact (Hartree-Fock) exchange mixed into the exchange part

of functional the Aiso constant becomes smaller. Absolute values of Aiso increase in order:

|Aiso(B)| < |Aiso(B3)| < |Aiso(BH)|

The eigenvalues of the square of the total electronic spin ⟨S2⟩, reported in the last

column of Table 3, show the same trend:

⟨S2⟩(B) < ⟨S2⟩(B3) < ⟨S2⟩(BH)

- 11 -

⟨S2⟩ increases with the increasing mixing of exact exchange into the functional. The Aiso

dependence on the correlation part of functional is much less pronounced, increasing in

order:

|Aiso(LYP)| < |Aiso(P86)| < |Aiso(PW91)|.

Table 3 HFC tensors (in MHz] of complex 1aa calculated at the DFT level with various functionals.

Aiso Tx Ty Tz ⟨S2⟩ b BLYP -107.1 -9.7 -128.6 138.2 0.7655 BP86 -119.1 -9.5 -125.2 134.6 0.7664

BPW91 -124.8 -9.5 -125.1 134.6 0.7680 B3LYP -140.0 -9.9 -136.2 146.1 0.7833 B3P86 -154.4 -9.7 -133.2 142.9 0.7854

B3PW91 -159.9 -9.6 -132.9 142.5 0.7881 BHLYP -189.1 -7.5 -133.0 140.5 0.8539 BHP86 -210.5 -7.5 -130.8 138.3 0.8544

BHPW91 -219.3 -7.2 -129.7 136.8 0.8644 exp. -207.2 -11.0 -140.0 151.0 --

a X-ray geometry [13]. b The spin contamination is reflected in the deviation of the ⟨S2⟩ from

the ideal value for a doublet ( 0.75).

The best agreement between experimental and calculated Aiso is found for BHP86

exchange-correlation functional (-207 and -211 MHz, respectively). However, all

calculations with BH exchange functional show the value of ⟨S2⟩ greater than 0.85. It is

apparent that calculated values of Aiso correlate with the spin-contamination. Among the

functionals employing the B3 exchange, that includes the smaller amount of exact

exchange, the B3PW91 gives Aiso closest to the experimental value (-160 MHz). The

agreement is significantly worse than found for BH exchange functional; however, the

spin-contamination is severally reduced (⟨S2⟩ = 0.79). The results obtained with purely

DFT description of electron exchange (B functional) show the smallest spin-

contamination, however, the agreement with experimental Aiso is worse (over 80 MHz

error). It remains to be seen whether such large spin-contamination is realistic and whether

these functionals can reproduce Aiso for other vanadocene derivatives. Therefore, the

calculations on other complexes were performed with only two exchange-correlation

functionals: (i) BHP86 functional that gives Aiso in fair agreement with experiment without

any scaling but it shows relatively large spin-contamination and (ii) B3PW91 functional

that shows only modest spin-contamination.

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2.4.2 HFC tensor of vanadocene compounds (X-ray geometries)

Part of the error in Aiso calculations can be due to the discrepancies between optimised

and experimental geometries. In order to evaluate the ability of DFT to predict HFC tensor,

the calculations on fourteen vanadocene complexes in experimental geometries are known

were carried out. The isotropic and anisotropic components of HFC tensors calculated at

the experimental geometries using BHP86 and B3PW91 exchange-correlation functionals

are summarized in Table 4. The BHP86 functional gives value of Aiso in relatively good

agreement with experiment, with the errors from –21 to +0.1 MHz. Although, significantly

less satisfactory agreement was found for B3PW91 functional, this error is relatively

constant.

Table 4 HFC tensors (in MHz) calculated with B3PW91 and BHP86 functionals at X-ray geometries.

Aiso(calc) Aiso(exp.)b Tx(calc) Ty(calc) Tz (calc) ⟨S2⟩ 1a a B3PW91 -159.9 -207.2 -9.6 -132.9 142.5 0.7881

BHP86 -210.5 -207.2 -7.5 -130.8 138.3 0.8544 2b B3PW91 -167.1 -212.5 -24.2 -125.6 149.8 0.7808

BHP86 -218.7 -212.5 -19.8 -125.3 145.1 0.8345 3a B3PW91 -154.6 -205.3 -16.8 -123.1 139.9 0.7775 BHP86 -206.3 -205.3 -1.8 -137.3 139.1 0.8245

4a B3PW91 -158.2 -199.7 -34.9 -117.6 152.5 0.7817 BHP86 -200.2 -199.7 -32.1 -121.7 153.8 0.8225

6a B3PW91 -163.7 -210.5 -18.0 -123.9 141.9 0.7817 BHP86 -222.8 -210.5 -13.0 -122.9 135.9 0.8465

6b B3PW91 -165.6 -211.3 -35.5 -111.2 146.7 0.7832 BHP86 -225.1 -211.3 -28.1 -112.5 140.6 0.8470

7c B3PW91 -158.6 -207.6 -12.5 -127.1 139.6 0.7826 BHP86 -213.0 -207.6 -9.1 -128.5 137.6 0.8402

8b B3PW91 -165.3 -208.1 -28.8 -119.6 148.4 0.7904 BHP86 -208.0 -208.1 24.5 114.9 139.3 0.8813

10a B3PW91 -175.5 -221.1 -13.9 -134.4 148.3 0.7841 BHP86 -229.2 -221.1 -13.6 -125.5 139.1 0.8496

11b B3PW91 -175.2 -222.2 -28.2 -123.6 152.0 0.7882 BHP86 -231.6 -222.2 -22.1 -117.8 139.9 0.8647

12a B3PW91 -147.3 -189.8 -56.0 -101.4 157.4 0.7818 BHP86 -196.9 -189.8 -50.1 -100.8 150.9 0.8321

15 b B3PW91 -164.7 -208.9 -39.2 -115.7 154.9 0.7844 BHP86 -218.7 -208.9 -30.1 -111.1 141.2 0.8541

18 c B3PW91 -142.8 -183.1 -33.3 -110.6 143.9 0.7888 BHP86 -204.1 -183.1 -24.9 -99.5 124.4 0.8790

19 c B3PW91 -147.5 -187.8 -28.0 -115.4 143.4 0.7880 BHP86 -206.9 -187.8 -21.0 -105.6 126.6 0.8704

X-ray geometries were taken from: a [13], b [14], c [15].

- 13 -

Correlation of calculated and experimental Aiso is presented in Fig. 6 for both

functionals. Aiso calculated at B3PW91 level using experimental structures correlate well

with experimental values:

Aiso(exp) = 1.14 Aiso(B3PW91) – 22.11 (1)

with the correlation coefficient R = 0.970 and standard deviation SD = 2.94.

Significantly worse correlation between Aiso experimental and calculated at the BHP86

level was found:

Aiso(exp) = 0.89 Aiso(BHP86) – 14.44,

with R = 0.834 and SD = 6.67.

Evidently, the B3PW91 functional gives Aiso with error of about 40 MHz. However, this

error is predictable and it depends on Aiso linearly. This error can be corrected using the

equation (1). In further discussion we will use the results obtained with B3PW91

functional corrected according to equation (1).

Fig. 6 Correlation of experimental and theoretical Aiso constants, calculated with

BHP86 at X-ray determined geometries (■) and with B3PW91 functional at

X-ray (+) and B3PW91 geometries (○).

2.4.3 HFC tensor of vanadocene compounds (optimised geometries)

For EPR spectra interpretation of complexes, which X-ray parameters are not available,

it is possible to use only optimised geometries. Thus, the geometries obtained at the DFT

- 14 -

level are used in HFC tensor calculations. To show the effect of the use of the optimised

geometry instead of the experimental geometry the Aiso calculated at optimised geometries

are also shown in Figure 6. Small deterioration of correlation was observed: R = 0.914 and

SD = 4.89.

A reasonable agreement between experimental and DFT geometries was found. The

differences in bond lengths do not exceed 0.07 Å and differences in valence angles are

smaller than 5o. The largest difference between experimental and theoretical geometries

was found for complexes 6a, 6b and 12a. Such complexes also show the largest difference

between Aiso calculated at experimental and theoretical geometries.

Fig. 7 Comparison of experimental and scaled Aiso constants of vanadocene complexes at

B3PW91 optimised geometries.

Experimental and calculated HFC tensors (B3PW91 level) for all 27 compounds are

compared in Table 5. Both, calculated Aiso and Aiso scaled according to equation (1)

(Aiso(scal)) are reported. Very good agreement between experimental and scaled Aiso was

found, with the largest deviation 9 MHz. This is depicted in Figure 7 (correlation

coefficient R = 0.949 and SD = 4.51 MHz). A good correlation is consistent with relatively

constant spin-contamination found for all compounds (spin-contamination in the range

0.024-0.041). A reasonable agreement between experimental and calculated (no scaling

applied) anisotropic part of HFC tensor was found.

- 15 -

Table 5 Comparison of experimental HFC tensors and those calculated at B3PW91 level at the B3PW91 optimised geometries (in MHz).

A iso(calc) Aiso(scal)a Aiso(exp) Tx(calc) Ty(calc) Tz(calc) Tx(exp Ty(exp) Tz(exp) ⟨S2⟩ ref.b 1a -159.9 -204.4 -207.2 -2.2 -138.1 140.3 -11.0 -140.0 151.0 0.7845 [16]2a -164.3

-209.4 -212.2 -10.8 -135.4 146.2 -7.8 -145.8 153.6 0.77802b -164.6 -209.8 -212.5 -15.3 -128.6 143.9 -- -- -- 0.77823a -152.6 -196.1 -205.3 -5.1 -130.2 135.3 -- -- -- 0.77814a -157.5 -201.7 -199.7 -14.7 -126.4 141.1 -- -- -- 0.77755a -133.5 -174.3 -169.8 -3.0 -128.3 131.3 -- -- -- 0.77356a -157.8 -202.0 -210.5 -10.3 -128.1 138.4 -- -- -- 0.77906b -159.6 -204.1 -211.3 -18.6 -121.6 140.2 -- -- -- 0.77917a -156.7 -200.7 -206.3 -15.2 -119.4 134.6 -- -- -- 0.7836 7c -158.3 -202.6 -207.6 - 8.2 -129.7 137.9 -- -- -- 0.7820 8a -166.6 -212.0 -209.3 -12.4 -134.0 146.4 -- -- -- 0.78418b -164.2 -209.3 -208.1 -28.8 -119.6 148.4 -- -- -- 0.79049a -172.2 -218.4 -220.3 1.7 -145.4 143.7 -16.2 -148.4 164.6 0.781910a -174.1 -220.6 -221.1 -2.7 -141.3 144.0 -16.1 -145.1 161.2 0.783711a -173.9 -220.4 -222.2 -3.6 -140.8 144.4 -19.4 -145.0 164.4 0.783911b -173.2 -219.6 -222.5 -12.3 -131.5 143.8 -27.8 -134.8 162.6 0.783212a -151.8 -195.2 -189.8 -55.8 -102.8 158.6 -52.0 -117.3 169.4 0.780013a -166.2 -211.6 -208.1 -50.8 -109.9 160.7 -47.0 -126.0 173.0 0.779014 -154.7 -198.5 -189.5 -0.8 -136.8 137.6 -- -- -- 0.7897 [17]15 -164.7 -209.9 -208.9 -41.9 -112.7 154.6 -34.0 -129.9 163.9 0.7863 [18]16 -163.7 -208.7 -209.9 -38.4 -112.5 150.9 -30.0 -131.9 161.9 0.7889 [18]17 -146.0 -188.6 -182.9 -54.9 -101.4 156.3 -- -- -- 0.7849 [19]18 -143.6 -185.8 -183.1 -33.5 -109.7 143.2 -- -- -- 0.7914 [15]19 -150.2 -193.3 -187.8 -27.1 -114.7 141.8 -- -- -- 0.7912 [15]20 -143.0 -185.1 -187.6 -53.2 -99.3 152.5 -42.6 -120.2 162.8 0.7844 [20]21 -143.7 -185.9 -187.3 -52.9 -99.7 152.6 -44.2 -119.0 163.2 0.7841 [20]22 -143.7 -185.9 -188.1 -53.1 -99.6 152.7 -43.2 -120.2 163.4 0.7842 [20]

a Aiso parameters scaled according to Eq. (1). b References of the experimental HFC tensors.

- 16 -

2.4.4 Using of HFC tensor calculations for structure investigation

Good agreement between experimental and calculated anisotropic components of HFC

tensor and excellent agreement between scaled and experimental Aiso justify the use of DFT in

interpretation of experimental HFC tensor of vanadocene complexes. Several examples are

shown below.

a) Acidoligand substitution

1a

VCl

Cl

9c

VCl

OOCH +9a

VOOCH

OOCH

EPR spectra obtained after partial precipitation of Cl- ions from aqueous solution of

vanadocene dichloride (1a) and formic acid, evaporation and dissolution in inert solvent

(CH2Cl2) are superposition of simple eight-line spectra of reactant (1a) two other vanadocene

compounds. Based on calculations it is possible to assign the Aiso parameters -213.5 and -

220.3 MHz to compounds 9c and 9a, respectively. The calculated Aiso constants (9c: Aiso(scal)

= 210.1 MHz; 9c: Aiso(scal) = 218.4 MHz) are in good agreement with experiment. Such

calculations proved the expectation that monosubstituted compound (9c) gives the EPR

parameters, which are the mean value of these for corresponding disubstituted compounds (1a

and 9a).

b) Donor atom assignment

2a1

VNCO

NCOV

OCN

OCN

2a2 Several structures can be expected, when vanadocene forms a complex with ligands, where

more than one donor atom can form a bond with vanadium. Such situation occurred for OCN-,

dca and dcnm ligands.

Cyanatane can be bonded either through oxygen or nitrogen can be a donor atom. Structure

2a1 is energetically more stable than structure 2a1 at the B3PW91 level (195 kJ/mol).

17

Calculated values of Aiso(scal) (-209.4 MHz) of structure 2a1 is in very good agreement with

experimental value (-212.2 MHz).

Table 6 HFC tensors (in MHz) of pseudohalide complexes.

Aiso(calc) Aiso(scal) Aiso(exp) E(kJ/mol) ⟨S2⟩ 2a1 calc. -164.3 -209.4 -- 0 0.7780 2a2 calc. -185.9 -234.0 -- 195 0.7888 2a exp. -- -- -212.2 -- -- 6a1 calc. -157.8 -202.0 -- 0 0.7790 6a2 calc. -161.0 -205.7 -- 98 0.7873 6a exp. -- -- -210.5 -- -- 8a1 calc. -151.5 -194.8 -- 111 0.7823 8a2 calc. -166.6 -212.0 -- 0 0.7841 8a exp. -- -- -209.3 -- --

For dca and dcnm ligands were proposed structures with ligands bonded through cyano

nitrogen (6a1 and 8a1, respectively) and through amide nitrogen (6a2) and nitroso oxygen

(8a2).

6a2

VN

N

N

N

N

N

8a2

VO

O

N

N

N

N

N

N8a1

VN

NN

N

NO

N

O

6a1

VN

N

N

N

N

N

Both coordination modes of such ligands give very similar values of the calculated Aiso

constant (see for Aiso(scal) in the Table 6). However, the real mode can be found based

comparison of their energetic stability. From data obtained, it is evident that dca ligand

prefers the bonding via cyano nitrogen (6a1), while the dcnm ligand bonding via nitroso

oxygen (8a2).

c) Interaction with bidentate ligands

When vanadocene fragment interacts with bidentate ligands (e. g., dicarboxylic acids) two

types of complexes can be formed: (i) chelate complex of single dicarboxylic acid with

18

vanadocene fragment (structures 12a1, 13a1 and 231) or (ii) complex of vanadocene fragment

with two molecules of dicarboxylic acid with monodentate bonds (structures 12a2, 13a2 and

232).

12a2, 13a2, 232

12a A =13a A = CH223 A = CH2CH2

VO

O

O

O

A

12a1, 13a1, 231

VO

O

OA COOH

OA COOH

Calculated HFC tensors for both types of complexes together with experimental data are

summarised in Table 7. Aiso(scal) obtained for chelate structures 12a1 and 13a1 are in good

agreement with experimental Aiso constants. In addition, calculated anisotropic parameters of

these complexes are in significantly better agreement with experimental parameters than those

calculated for complexes 12a2 and 13a2. Therefore, it can be concluded that complex of

vanadocene with oxalic and malonic acids forms a chelate compound. This is in agreement

with the results of X-ray diffraction analysis performed for complex 12a. With the increasing

size of dicarboxylic acid the difference between Aiso parameters of complexes with chelate

and monodentate bonds becomes smaller. The structure of complex 23 cannot be assigned

based on Aiso parameters calculated for two possible complex types (see Table 7). However,

two structural types can be distinguished based on the differences in anisotropic components

of HFC tensor.

Table 7 Calculated and experimental HFC tensors (in MHz) for the vanadocene complexes

of dicarboxylic acids.

Aiso(calc) Aiso(scal) Aiso(exp) Tx Ty Tz ⟨S2⟩ 12a1 calc. -151.8 -195.2 -- -55.8 -102.8 158.6 0.7800 12a2 calc. -172.7 -219.0 -- -3.1 -141.2 144.3 0.7831 12a exp. -- -- -189.8 -52.0 -117.3 169.4 -- 13a1 calc. -166.2 -211.6 -- -50.8 -109.9 160.7 0.7790 13a1 calc. -172.3 -218.5 -- 1.4 -145.4 144.0 0.7821 13a exp. -- -- -208.1 -47.0 -126.0 173.0 -- 231 calc. -172.8 -219.1 -- -40.3 -117.5 157.8 0.7821 232 calc. -172.3 -218.5 -- 1.4 -145.4 144.0 0.7821

19

2.5 Super-hyperfine coupling tensor

EPR signal of the paramagnetic compounds can be split by magnetic active nuclei of the

ligands. This effect, super-hyperfine coupling (S-HFC), is very important effect for structure

investigation of the paramagnetic compounds.

The S-HFC tensor was calculated for three vanadocene complexes (24, 25 and 26), for

which was previously observed the strong coupling with 31P (I = 1/2, 100%) [21, 22].

++

26

PV

Me

Ph

MePh

+

24

SV

SP

O

O

Et

Et25

SV

SP

Et

Et

The calculations of the aiso constant were performed using B3PW91 functional and

DZP/DZ/DZ basis set (Table 8). The optimised geometries (UB3PW91/DZP/DZ) were used

for these calculations.

Table 8 Calculated and experimental values of the aiso(31P) (in MHz).

aiso(calc) UB3PW91

aiso(calc) ROB3PW91 ⟨S2⟩ a aiso(exp)

24 152.9 111.3 0.7968 122.9 25 90.0 66.7 0.7981 83.9 26 -109.2 13.7 0.7807 -65.4

a ⟨S2⟩ value for UB3PW91 calculation.

Complexes with four membered chelate rings 24 and 25 have the magnetic active nuclei,

which cause S-HFC, at the twofold axis. The non-bonded distances V–P for complexes 24

and 25 were found 3.14 and 3.20 Å. respectively. Structure of complex 26 is different. The S-

HFC is caused by nucleus that is with the donor atom of the ligand that is coordinated to the

vanadocene moiety. The bond distance V–P is 2.60 Å.

DFT calculations show that the SOMO orbital contribution to the aiso value is negligible.

This parameter is given mainly by spin polarized core orbitals. This conclusion is further

supported results obtained at the restricted open-shell level (ROB3PW91) that neglect the spin

polarization effect.

Different situation was found for complexes 24 and 25. The high values obtained at

ROB3PW91 level show that large contribution of the SOMO orbital. Hence, the aiso constant

is given by contribution of both SOMO and spin polarized core orbitals.

20

The calculated values of the |aiso(31P)| are largely overestimated (0 - 71%). Thus, such

calculations cannot be used for estimation of the exact value of the aiso constant. DFT gives

only for qualitative description of the S-HFC. They can be used for the prediction of the

appearance S-HFC in the EPR spectra of vanadocene complexes.

2.5.1 Using of S-HFC calculations for structure investigation

a) The proving of the bonding mode for phosphate and carbonate ligands

271

OV

O

POH

POH

OOH

OOH272

OV

OP

O

OH282

OV

O

CO

OH

C OHO

281

OV

OC O

Based on DFT calculations, it is possible to predict the appearance of the S-HFC in the

EPR spectrum. Such method was used for structure proving of the complexes that are formed

by reaction of the vanadocene dichloride (1a) with phosphates and carbonates. Two structure

types were proposed for interaction with these ligands: i) chelate structures (271 and 281) ii)

structures with monodentate bonded ligand (272 a 282). The calculations show that only

chelate complexes 271 and 281 can split EPR signal by nuclei of the ligands (31P, 13C). The

previously made calculations indicate that calculated aiso is largely overestimated. In the case

of the carbonate complex 281 the S-HFC should be at the detection limit of the EPR

spectroscopy.

Table 9 Comparison of calculated value of the aiso constants (in MHz) with experiments.

aiso(calc) UB3PW91

aiso(calc) ROB3PW91 ⟨S2⟩ a aiso(exp)

271 calc. 142.4 118.4 0.7800 -- 272 calc. 12.3 13.3 0.7872 -- 27 exp. -- -- -- 81.5 281 calc. 37.5 28.2 0.7791 -- 282 calc. 4.4 4.6 0.7838 -- 28 exp. -- -- -- 24.1

a ⟨S2⟩ value for UB3PW91 calculation.

Phosphate complex 27 was prepared by reaction of the complex 1a with Na2HPO4. The

reaction of 1a with sodium carbonate labeled by 13C (I = 1/2, 99%) was used for preparation of

21

the complex 28. Both complexes give the EPR spectra with super-hyperfine coupling on

doublet 1:1 (see Figs. 8 and 9). The S-HFC of complexes 27 and 28 is caused by nucleus 31P

(I = 1/2, 100%) and 13C (I = 1/2, 99%), respectively. The complex 28 gives weak S-HFC (|aiso|

= 24.1 MHz). This one is distinct at the first line of the spectrum and its derivation (Fig. 10).

Fig. 8 EPR spectrum of the complex 27 (ν = 9.451 GHz).

Fig. 9 EPR spectrum of the complex 28 with carbonate ligand labeled by 13C (ν = 9.453 GHz).

a) b)

Fig. 10 EPR spectrum of the complex 28 with carbonate ligand labeled by 13C (ν = 9.453 GHz).

a) The first line of the EPR spectrum. b) Second derivation of the absorption band.

22

b) The proving of the structure for the cyanide complex 5a

5a

VCN

CN

The structure of the complex 5a was proposed based on spectroscopic measurements. The

substitution of the chloride ligands with cyanides was proved by infrared and Raman

spectroscopy. Such substitution was accompanied with large changes of EPR parameters

(Aiso, giso). The performed DFT calculations show that complex 5a should give strong S-HFC

by nuclei of 13C of the cyanide ligands (aiso(UB3PW91) = -50.6 MHz). This expectation was

experimentally proved.

The figures 11 and 12 show the EPR spectra of the complexes that were prepared by

reaction of the vanadocene dichloride (1a) with K12CN a K13CN, respectively. Complex

Cp2V(13CN)2 gives strong S-HFC (1:2:1) that is caused by two equivalent nuclei of 13C

(aiso(exp) = -44.7 MHz). Such experiment unambiguously proves the substitution of both

chlorides by cyanide ligands.

Fig. 11 EPR spectrum of the complex Cp2V(12CN)2 (ν = 9.453 GHz).

Fig. 12 EPR spectrum of the complex Cp2V(13CN)2 (ν = 9.453 GHz).

23

3. Conclusions

Based on results, which are discussed in this work, EPR spectroscopy is very useful

method for structure investigation of the paramagnetic vanadocene compounds. Especially,

the HFC tensor gives important information about the coordination sphere of the central

metal.

Preparation of 23 new vanadocene complexes is described in this work. The X-ray

structure analysis was done for 10 complexes. Experimental EPR spectroscopic data were

obtained for all prepared complexes.

Hyperfine coupling of vanadocene complexes was studied by DFT methods. The very

good agreement was found for Aiso constant that was calculated using B3PW91 functional

(DZP/DZ basis set) and scaling using equation 1. The anisotropic part ( ) is in good

agreement with experiment (without scaling). It was shown that experimental obtained HFC

tensors together with DFT calculations could conclude about the proposed complex structure.

T~

Super-hyperfine coupling (S-HFC) is further important effect that gives important

information about the complex structure. Appearance of the S-HFC was predicted and

subsequently experimentally proved for some vanadocene compounds.

Experimental and theoretically obtained data proved that substitution of the acido-ligands

largely influence the HFC tensor of the vanadocene compounds. The largest changes in Aiso

constant were found for reaction, in which the donor atom of the acido-ligand is changed or

chelate ring appears. The S-HFC was observed only for compounds, in which the magnetic

active nucleus is bonded to the central metal (compound 5a), and for compounds wit four

membered chelate ring (compounds 27 a 28).

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Abbreviations used in text

A~ - hyperfine coupling tensor

Aiso - isotropic hyperfine coupling constant

acac - acetylacetonate

bpy - 2,2'-bipyridine

Cp - cyclopentadienyl, η5-C5H5

25

Cp' - methylcyclopentadienyl, η5-CH3C5H4

Cg - centroid of the Cp ring

dca - dicyanamide

dcnm - dicyanonitrosomethanide

DFT - Density Functional Theory

EPR - Electron Paramagnetic Resonance

g~ - g-tenzor

giso - isotropic g-factor

HFC - hyperfine coupling

hfpd - hexafluorpentadionate

I - nuclear spin

IR - Infrared Spectroscopy

Me - methyl

phen - 1,10-phenathroline

i-Pr - isopropyl

RO - "restricted open shell"

⟨S2⟩ - the squared value of the total electronic spin

T~ - anisotropic part of the HFC tensor

tcm - tricyanomethanide

trop - 2-hydroxy-2,4,6-cyclohexatriene-1-onate

S-HFC - super-hyperfine coupling

U - "unrestricted"

Papers Published by Author:

1. J. Honzíček, P. Nachtigall, I. Císařová J. Vinklárek, Synthesis, characterization and

structural investigation of the first vanadocene(IV) carboxylic acid complexes prepared

from the antitumor agent vanadocene dichloride, J. Organomet. Chem. 2004, 689, 1180-

1187.

2. J. Vinklárek, H. Paláčková, J. Honzíček, Experimental and theoretical study of the first

vanadocene(IV) complexes of α-amino acid prepared from the antitumor agent

vanadocene dichloride, Collet. Czech. Chem. Commun. 2004, 69, 811-821.

26

3. J. Honzíček, J. Vinklárek, M. Erben, I.Císařová, µ2-Oxo-bis[azido-bis(η5-

cyclopentadienyl)-titanium(IV)], Acta Cryst. 2004, E60, m1090-1091.

4. J. Vinklárek, J. Honzíček, J. Holubová, Interaction of the antitumor agent vanadocene

dichloride with phosphate buffered saline, Inorg. Chim. Acta 2004, 357, 3765-3769.

5. J. Vinklárek, J. Honzíček, J. Holubová, An experimental and theoretical study of the

Cp2VO2CO: the first observation of 13C super-hyperfine coupling of metallocene

complexes, Magn. Reson. Chem. 2004, 42, 870-874.

6. J. Honzíček, J. Vinklárek, P. Nachtigall, A density functional study of EPR hyperfine

coupling for vanadocene (IV) complexes, Chem. Phys. 2004, 305, 291-298.

7. J. Honzíček, J. Vinklárek, M. Erben, I. Císařová, Bis(η5cyclopentadienyl)-bis(N-

thiocyanato)-vanadium(IV), Acta Cryst. 2004, E60, m1617-1618.

8. J. Honzíček, I. Císařová and J. Vinklárek Acetonitrile-chloro-bis(η5-cyclopentadienyl)-

vanadium(IV) tetrachloro-iron(III), Acta Cryst. 2005, E61, m149-151.

9. J. Honzíček, M. Erben, I. Císařová, J. Vinklárek, Synthesis Characterization and

Structure of Metallocene Dicyanoamide Complexes, Inorg. Chim. Acta 2005, 358, 814-

819.

10. J. Vinklárek, J. Honzíček, J. Holubová, Inclusion compounds of cytostatic active

(C5H5)2VCl2 and (CH3C5H4)2VCl2 with α-, β-and γ- cyclodextrines: Synthesis, EPR

study and Investigation of the Antimicrobial Behavior toward Escherichia coli., Centr.

Eur. J. Chem. 2005, 3, 72-81.

11. J. Vinklárek, J. Honzíček, I. Císařová, M. Pavlišta, J. Holubová, Synthesis,

Characterization and Structure of the Bis(methyl-cyclopentadienyl)vanadium(IV)

Carboxylates, Centr. Eur. J. Chem. 2005, 3, 157-168.

12. J. Honzíček, M. Erben, I. Císařová, J. Vinklárek, Bis(η5-methyl-cyclopentadienyl)-

bis(cyanato)-vanadium(IV), Appl. Organomet. Chem. 2005, 19, 100-101.

13. J. Honzíček, M. Erben, I. Císařová, J. Vinklárek, Bis(η5-cyclopentadienyl)-bis(azido)-

vanadium(IV), Appl. Organomet. Chem. 2005, 19, 102-103.

14. J. Honzíček, I. Císařová, J. Vinklárek, Bis(3-methyl-2-cyclopenten-1-one)dichloro-

oxovanadium(IV), Appl. Organomet. Chem. 2005, 19, 692-693.

15. J. Honzíček, H. Paláčková, I. Císařová, J. Vinklárek, Ansa-vanadocene complexes with

short interannular bridge, J. Organomet. Chem. 2005 (accepted).

27

16. J. Vinklárek, H. Paláčková, J. Honzíček, M. Holčapek, I. Císařová, Investigation of

vanadocene(IV) α-amino acids complexes, Synthesis, structure and behavior in

physiological solutions, human plasma and blood, Inorg. Chem. 2005 (submitted).

Conferences (International)

Lectures:

1. J. Honzíček, J. Vinklárek and P. Nachtigall, An EPR Study of

Bis(cyclopentadienyl)vanadium Carboxylates, 19th International Conference on

Coordination and Bioinorganic Chemistry, Smolenice, Slovakia, 2.-6.6.2003.

2. J.Honzíček, J.Vinklárek and P. Nachtigall, A Structural Study of

Bis(cyclopentadienyl)vanadium Carboxylates, 8th Seminar of PhD Students on

Organometallic Chemistry, Hrubá Skála, Czech Republic, September 29.9-3.10.2003.

3. J. Honzíček, M. Erben, P. Nachtigall and J. Vinklárek, Vanadocene(IV) Pseudohalide

Complexes: Structural study, 4th International Symposium on Chemistry and Biological

Chemistry of Vanadium, Szeged, Hungary, 3.-5.9.2004.

4. J. Honzíček, J. Vinklárek and P. Nachtigall, A theoretical and experimental study of

EPR hyperfine coupling of vanadocene(IV) conplexes, 9th Regional Seminar of PhD-

Students on Organometallic and Organophosphorous Chemistry, Szklarska Poręba,

Poland, 10-14.4. 2005.

5. J. Honzíček, P. Nachtigall and J. Vinklárek, Hyperfine and Super-hyperfine Coupling of

Vanadocene(IV) Complexes, 20th International Conference on Coordination and

Bioinorganic Chemistry, Smolenice, Slovakia, 5.-10.6.2005.

Posters:

1. J. Vinklárek, M. Erben, A. Růžička, R. Jambor, J. Honzíček: Study of Electonic

Structure Titanocene Dihalides, XII FECHEM Conference on Organometallic

Chemistry, Gdaňsk, Poland, 2.-7.9.2001.

2. J. Honzíček, J. Vinklárek, J. Holubová and P. Nachtigall, A Study of Interaction of

Vanadocene Fragment with Proteins on the Model Systems, 19th International

Conference on Coordination and Bioinorganic Chemistry, Smolenice, Slovakia, 2.-

6.6.2003.

28

3. J. Honzíček, J. Vinklárek, P. Nachtigall, EPR Hyperfine Coupling of Vanadocene(IV)

Compounds: Theoretical Study, 4th International Symposium on Chemistry and

Biological Chemistry of Vanadium, Szeged, Hungary, 3.-5.9.2004.

4. J. Honzíček, H. Paláčková, J. Holubová, I. Císařová, J. Vinklárek, Synthesis and

Characterization of Vanadocene(IV) Amino Acid Complexes, 4th International

Symposium on Chemistry and Biological Chemistry of Vanadium, Szeged, Hungary, 3.-

5.9.2004.

5. J. Holubová, J. Vinklárek, J. Honzíček, Inclusion Compounds of Vanadocene Dichloride

and Cyclodextrines: an ESR Study, Solid State Chemistry 2004, Prague, Czech

Republic, 12.-17.9.2004.

Conferences (National)

Lectures:

1. J. Honzíček, J. Vinklárek and P. Nachtigall, The interaction of cytostatic active

vanadocene dichloride with bioligands, 55th Congress of the Chemical Societies,

Košice, Slovakia, 8.-12.9.2003.

2. J. Vinklárek, J. Honzíček and J. Holubová, A Study of cancerostatic active Cp2VCl2 by

EPR spectroscopy, 55th Congress of the Chemical Societies, Košice, Slovakia, 8.-

12.9.2003.

3. J.Honzíček, J.Vinklárek, P. Nachtigall and I.Císařová, A study of the pseudohalide

complexes of the type Cp2VX2, 56th Congress of the Chemical Societies, Ostrava,

Czech Republic, 6.-9.9.2004.

4. H. Paláčková, J. Vinklárek, J. Honzíček, J. Holubová, A study of derivatives of

vanadocene dichloride and their effect on the cell division, 56th Congress of the

Chemical Societies, Ostrava, Czech Republic, 6.-9.9.2004.

Posters:

1. J. Honziček, J. Vinklárek, M. Erben and P. Nachtigall, Assignment of the UV-VIS

spectra of d0 complexes Cp2TiX2 (X = F, Cl, Br, I) using the density functional methods.

54th Congress of the Chemical Societies, Brno, Czech Republic, 30.6.-4.7.2002.

29

2. J. Vinklárek, J. Honziček and P. Nachtigal, Theoretical study of the bonding of d0

complexes Cp2TiX2 (X = F, Cl, Br, I), 54th Congress of the Chemical Societies, Brno,

Czech Republic, 30.6.-4.7.2002.

3. J. Honziček, J. Vinklárek, J. Holubová: A study of the derivatives of titanocene

dichloride and vanadocene dichloride with anticancer effect, 54th Congress of the

Chemical Societies, Brno, Czech Republic, 30.6.-4.7.2002.

4. H. Paláčková, J.Vinklárek and J.Honzíček, A Study of Interaction of Vanadocene

Fragment with Proteins on the Model Systems, 55th Congress of the Chemical

Societies, Košice, Slovakia, 8.-12.9.2003.

5. J. Honzíček, J. Vinklárek and I. Císařová, An EPR study of

Bis(cyclopentadienyl)vanadium Carboxylates, 55th Congress of the Chemical Societies,

Košice, Slovakia, 8.-12.9.2003.

6. H. Paláčková, J. Zemanová, J. Vinklárek and J. Honzíček, A Study of inclusive

compounds of the cytostatic active Cp2'VCl2 with cyclodextrines by EPR spectroscopy,

55th Congress of the Chemical Societies, Košice, Slovakia, 8.-12.9.2003.

7. J. Honzíček, J. Vinklárek and J. Holubová, Hydrolysis of vanadocene dichloride and

interaction with carbonates, 55th Congress of the Chemical Societies, Košice, Slovakia,

8.-12.9.2003.

8. J. Vinklárek, J. Honzíček and J. Holubová, Interaction of vanadocene fragment with the

components of PBS solution that is used for preclinical tests, 55th Congress of the

Chemical Societies, Košice, Slovakia, 8.-12.9.2003.

9. J. Vinklárek, J. Honzíček, M. Erben, I. Pavlík, Ligand Field Theory and d-d Spectra of

Bent d1 metalocenes, 55.zjazd chemických společností, 8.-12.9.2003, Košice, Slovakia.

10. J. Vinklárek, J. Honzíček, I. Císařová and J. Holubová, Synthesis, Characterization and

Structure of the Bis(methyl-cyclopentadienyl)vanadium(IV) Carboxylates, 56th

Congress of the Chemical Societies, Ostrava, Czech Republic, 6.-9.9.2004.

11. J. Vinklárek, H. Paláčková, J. Honzíček and P. Svobodová, A study of the derivatives of

vanadocene dichloride with amino acids with sulphur in side-chain. 56th Congress of

the Chemical Societies, Ostrava, Czech Republic, 6.-9.9.2004.

12. J. Honzíček, M. Erben, P. Nachtigall and J. Vinklárek, Vanadocene(IV) pseudohalide

complexes, 56th Congress of the Chemical Societies, Ostrava, Czech Republic, 6.-

9.9.2004.

30

13. J. Honzíček, J. Vinklárek, P. Nachtigall, A theoretical study of EPR hyperfine coupling

of vanadocene(IV) compounds, 56th Congress of the Chemical Societies, Ostrava,

Czech Republic, 6.-9.9.2004.

14. J. Vinklárek, J. Honzíček, P. Nachtigall and Z. Černošek, An experimental study of

antitumor active vanadocene(IV) complexes, 56th Congress of the Chemical Societies,

Ostrava, Czech Republic, 6.-9.9.2004.

15. J. Honzíček, J. Vinklárek, M. Svitač and B. Frumarová, Synthesis and characterization

of ansa-vanadocene(IV) compounds, 56th Congress of the Chemical Societies, Ostrava,

Czech Republic, 6.-9.9.2004.

16. H. Paláčková, J. Honzíček, J. Vinklárek and B. Frumarová, Synthesis and

characterization of vanadocene complexes of a-amino acids, 56th Congress of the

Chemical Societies, Ostrava, Czech Republic, 6.-9.9.2004.

17. H. Paláčková, J. Vinklárek and J. Honzíček, Biological activity of complexes of the type

[Cp2V(aa)]Cl on Escherichia coli, 56th Congress of the Chemical Societies, Ostrava,

Czech Republic, 6.-9.9.2004.

18. M. Erben, J. Vinklárek, I. Císařová and J. Honzíček, Synthesis and structures of µ-oxo

titanocene compounds with pseudohalide ligands, 56th Congress of the Chemical

Societies, Ostrava, Czech Republic, 6.-9.9.2004.

31