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Статья
Paper
DFT B3LYP Quantum-Chemical Calculation of Molecular Structures of (6.6.6)Macrotricyclic M" Complexes with (N,N,N,N)-Coordinatmg Ligand Formed in the MII-Hydrazinomethanethiohydrazide-Propanone Triple Systems
Denis V. Chachkovb and Oleg V. Mikhailova@
aKazan State Technological University, 420015 Kazan, Russia
hKazan Branch of Interdepartmental Super-Computer Center of RAS, 420008 Kazan, Russia Corresponding author E-mail: ovm@kstu.ru
Using DFT B3LYP method with 6-31G(d) basis set and the Gaussian 98 program, a calculation of geometric parameters of Mn11, Fe11, Co11, Ni11, Cu11 and Zn11 complexes with the tetradentate ligand - 4,6,6-trimethyl-2,3,7,8-tetraazanonen-3-dithiohydrazide-1,9 with NNNN-coordination of donor centres formed as a result of template processes in the M11-hydrazinomethanethiohydrazide-propanone triple systems, was carried out. The bond lengths and angles between various atoms in each of above-mentioned complexes is presented. It is noted that the additional 6-membered metalchelate cycle formed as a result of template "stitching", is not planar and is turned round with respect to the two 6-membered cycles on rather considerable angle; moreover, none of the chelate cycles in these complexes is plane.
Keywords: Macrocyclic complex, template synthesis, molecular structure, DFT B3LYP method.
Introduction
Previously we have reported[1-3] on the template syntheses in the M11 ion-hydrazinomethanethiohydrazide [H2N-NH-C(=S)-NH-NH2]-propanone H3C-C(=O)-CH3 triple systems proceeding into metalhexacyanoferrate(Il) gelatin-immobilized matrix implants (MHF-GIM, M = Co, Ni, Cu). Some details concerning the coordination of ligands formed as a result of such syntheses (what is known as chelating agent), to the corresponding metal ion were also established. According to mass-spectroscopy data, among other products of such synthesis, (6.6.6)macro-tricyclic met-alcomplexes (I) with 4,6,6-trimethyl-2,3,7,8-tetraazanonen-3-dithiohydrazide-1,9, are present in small amounts. Such metalmacrocyclic species are formed in the corresponding GIM according to the probable general reaction (1)
The three-dimensional structure of metalmacrocyclic compounds (I) is an open question up to now because attempts to obtain their crystals suitable for X-ray diffraction analysis, from gelatin matrix, were unsuccesful. In this connection, it appears expedient to carry out calculation of geometrical parameters of metalcomplexes formed in the systems under examination, using any of the modern quantum-chemical
methods able to provide independent objective data about their parameters. One such method is the hybrid method of density functional theory - DFT B3LYP; the present paper is devoted to enumeration and discussion of results of quantum-chemical calculation using this method.
Method
The B3LYP 6-31G(d) method, which is the hybrid DFT method using Becke function (1988) including Slater exchange, by beginning with amendment including density gradient, and correlation functional of Lee, Yang and Parr, which includes local and non-local therms,[4,5] was used by us for calculations. The energy values E were calculated according to the equation:
E = V + <hP> + 1/2<PJ(P)> + EX[P] + EC[P],
where V is nuclear energy of repulsion, <hP> - one-electronic (kinetic + potential) energy, 1/2<PJ(P)> - energy of electron repulsion, EX[P] - exchange functional; EC[P] - correlation functional. The 6-31G(d) basis, set where each inner atom orbital (AO) is described by six functions of Gaussian type (GTO), valence 2s AO- by three GTO, valence p-AO - by one GTO, with addition of polarization d-GTO to each p-function, was used. Conformity of the found stationary points to energy minima in all cases was proved by calculation of the second derivatives of energy on
h2n nh2
M2[Fe(CN)6] +2HN-C-NH +2 H3C-C-CH3+4 OH S О
HN-NH KM-NH
4-
S + fFe(CNU +6H„0 (1)
co-ordinates of atoms. Each equilibrium structure corresponding to points of a minimum on surfaces of potential energy, had only material values of frequencies. No limitation in symmetry was imposed on calculated complexes. All calculations were performed using the Gaussian 98 program.161 The time required to complete the quantum-chemical calculations of complexes studied was 6-7 months.
Results and Discussion
The molecular structures of given template complexes obtained as a result of quantum-chemical calculations, are presented on the Figures 1-6. As may be seen, the complexes under examination have quasi-tetrahedral coordination of donor centers around M11 central ion. According to the data of these calculations, metalmacrotricyclic coordination compounds (I) of Mn11, Co11 and Ni11 are high-spin complexes (spin multiplicity of basic state is 6, 4 and 3, respectively). The basic states of Cu11 and Zn11 compounds are spin doublet and spin singlet, respectively. At the same time it is particularly interesting that the Fe11 coordination compound with the ligand studied is intermediate-spin, as the spin multiplicity of its ground state is 3. It should be noted in this connection that in the case of the Ni11 complex the difference between the energy of the ground state (spin triplet) and the energy of the nearest excited state (spin singlet) is only 0.9 kJ, and, in principle, spin-isomeric coordination compounds may be expected in this case. The data concerning energies of states with various MS are presented in the Table 1.
As may be seen (Figures 1 - 6), in all compounds of type (I) under examination the grouping of four nitrogen
atoms forming the chelate unit MN4 is not planar. Besides, significantly, the sum of angles Z(N1)(N2)(N6), Z(N2) (N6)(N5), Z(N6)(N5)(N1) and Z(N5)(N1)(N2), as a rule, is considerably smaller than 360.00° [this sum is equal to 311.1o (Mn), 351.6o (Fe), 326.8o (Co), 309.6o (Ni), 314.7o (Cu) and 294.5o (Zn)]. The distances between neighboring nitrogen atoms in the chelate unit MN4 are extremely different from each other. It is natural that the MN4 chelate unit is not planar itself, too - in all cases the sum of valence angles Z(N1) (M1)(N2), Z(N2)(M1)(N6), Z(N6)(M1)(N5) and Z(N5) (M1)(N1) (VAS) is larger than 360o [376.3o (Mn), 364.3o (Fe), 377.7o (Co), 388.2o (Ni), 384.9o (Cu), 395.8o (Zn)], suggesting quasi-tetrahedral coordination of nitrogen donor atoms around MII. Incidentally, in each of the complexes considered, the four M-N bonds can be divided in two pairs of different lengths; as for distances between neighboring nitrogen atoms in the chelate units and for ZNMN valence angles, they all differ between themselves (Table 2). Upon going from Mn to Fe, the M-N bond lengths decrease, while from Fe to Co - increase, from Co to Ni - decrease again and from Ni to Zn, in a whole, increase again. The two kinds of M-N bonds indicated are fully expected: one is with «anionic» nitrogen atoms (N5) and (N6) (shorter), the other is with neutral nitrogen atoms (N1) and (N2) (longer). At the same time, the distances between M and nitrogen atoms (N3), (N4), (N7) and (N8) are relatively large - 285305 pm (Table 2) suggesting only very weak interaction. All the additional six-membered metalcycles formed as a result of template "stitching", are extremely distorted - there are no sets
Table 1. Relative energies in the ground and in the excited states with variousM values in metalmacrotricyclic compounds of type (I).
M11 Electron configuration Relative energies for states with various spin multiply M, kJ/mol*
1 2 3 4 5 6
Mn11 3d5 - 111.6 - 51.7 - 0
Fe11 3d6 82.8 - 0 - 9.3 -
Co11 3d7 - 10.3 - 0 - 145.8
Ni11 3d8 0.9 - 0 - - -
Cu11 3d9 - 0 - 151.1 - -
Zn11 3d10 0 - 155.8 - - -
* " - " non-existing spin states for given Mn.
Figure 1. Three-dimenisonal structure of the Mn11 complex of type (I), front view.
Figure 2. Three-dimenisonal structure of the Fe11 complex of type (I), front view.
H17
Figure 3. Three-dimenisonal structure of the Co11 complex of type (I), front view.
H12
Figure 4. Three-dimenisonal structure of the Ni11 complex of type (I), front view.
even of four atoms arranged in the same plane, in any of them. At the same time, any of these additional six-membered cycles is not itself planar - the (C7) carbon atom contained in it, is deflected from the N-CH2-CH2 group by a considerable angle [torsion angles Z(C7)(C3)(N2)(C4) and Z(C7)(C4)(N1)(C3), which may be considered as a measure of this deflection, are 37.2o and 38.4o in the case of Mn11 complex, 11.6o and 28.7o in the case of the Fe11 complex, 17.2o and 34.0o in the case of the Co11 complex, 19.6o and 34.0o in the case of Ni11 complex, 20.4o and 34.4o in the case of the Cu11 complex and 16.8o and 32.7o - in the case of Zn11 complex. It is noteworthy that in the case of the MnII complex, the values of given torsion angles are practically equal whereas in the case of all the other complexes studied, they differ essentially from each other.
Inthe free ligand, 4,6,6-trimethyl-2,3,7,8-tetraazanonen-3-dithiohydrazide-1,9, the N-N-bond lengths (N1)(N4), (N2) (N3), (N6)(N7) and (N5)(N8) are 141.7, 136.9, 141.8 and 141.7 pm, N-N distances between neighboring nitrogen atoms (N1)(N2), (N2)(N6), (N6)(N5) and (N5)(N1) - 324.3, 277.4, 308.8 and 286.5 pm, respectively. As may be seen from these data, the values of N-N-bond lengths in the free ligand are similar to the ones in the complexes under examination,
Figure 5. Three-dimenisonal structure of the Cu11 complex of type (I), front view.
Figure 6. Three-dimenisonal structure of the Znn complex of type (I), front view.
whereas the values of N-N distances between neighboring nitrogen atoms (N1)(N2), (N2)(N6), (N6)(N5) and (N5)(N1) are appreciably different from similar parameters for the given complexes.
The data of quantum-chemical calculation of values of standard thermodynamic parameters of metalmacrotricyclic compounds (I) under examination are presented in the Table 3. As may be seen, AG0f298 values for almost each of these complexes are large and considrably positive, which is an indication on their comparatively small stability. In addition, the largest AG0f298 value was calculated for the Fe" complex, and the smallest one for ZnII complex. Besides, thermodynamic characteristics of the considered complexes differ only slightly from the values for the free ligand 4,6,6-trimethyl-2,3,7,8-tetraazanonen-3 -dithiohydrazide-1,9 (see Table 3).
According to the data of our calculations, all complexes with 4,6,6-trimethyl-2,3,7,8-tetraazanonen-3-dithiohydrazide-1,9 examinated here have extremely high electric dipole moments - 3.75 (in the case of the Mnn complex), 6.29 (Fen complex), 5.20 (Con complex), 5.96 (Nin complex), 6.12 (Cun complex) and 5.24 (Znn complex)
Table 2. M-N and N-N bond lengths and ZNMN valence angles in metalmacrotricyclic compounds of type (I).
M Mn Fe Co Ni Cu Zn
M-N hond lengths, pm
(M1)(N1) 227.9 202.3 212.0 208.4 202.9 213.3
(M1)(N2) 224.5 200.9 206.9 202.7 203.6 209.7
(M1)(N5) 198.2 185.2 188.3 185.8 188.9 190.3
(M1)(N6) 199.3 184.9 189.1 186.7 188.8 191.2
Non-honding M-N distances, pm
(M1)(N3) 287.5 293.9 290.7 284.1 287.8 284.4
(M1)(N4) 303.5 294.0 297.3 292.5 287.4 290.0
(M1)(N7) 301.6 291.2 293.7 292.0 287.8 291.8
(M1)(N8) 304.5 291.7 293.0 293.0 290.7 291.7
ZNMN valence angles, grad
Z(N1)(M1)(N2) 85.0 91.9 92.2 92.0 93.9 87.9
Z(N2)(M1)(N6) 85.4 92.7 90.5 90.0 92.7 90.0
Z(N6)(M1)(N5) 128.6 88.0 103.7 114.9 103.5 125.5
Z(N5)(M1)(N1) 87.3 91.7 91.3 91.1 94.8 93.3
N-N hond lengths, pm
(N1)(N4) 144.4 144.4 144.1 143.9 143.6 144.1
(N2)(N3) 139.0 138.7 139.7 139.6 137.3 140.7
(N6)(N7) 139.8 139.1 139.0 139.1 140.0 140.1
(N5)(N8) 139.6 139.5 139.1 138.9 140.1 139.9
N-N distances between neighboring nitrogen atoms in the chelate unit MN4, pm
(N1)(N2) 305.6 289.6 301.8 295.7 297.0 293.7
(N2)(N6) 287.9 279.3 281.5 275.6 284.2 283.9
(N6)(N5) 358.2 257.2 296.8 314.0 296.6 339.1
(N5)(N1) 297.9 278.3 286.6 281.8 288.7 294.0
Table 3. Standard thermodynamical parameters of M11 complexes with 1,8-dioxa-3,6,10,13-tetraazacyclo-tetradecanetetrathione-4,5,11,12.
Standard thermodynamical parameters of formation Standard thermodynamical parameters of atomization
M kJ/mole S0 f, 298' J/mole-K kJ/mole ARa1 298 kJ/mole Sat S 298, J/mole-K AGat 298 kJ/mole
Mn 700.7 746.4 976.5 13575.8 4314.9 12289.3
Fe 763.9 729.4 1043.3 13648.5 4338.7 12354.9
Co 717.4 738.1 995.1 13703.2 4329.1 12412.5
Ni 728.8 737.1 1006.7 13696.6 4332.7 12404.8
Cu 626.8 729.9 907.8 13707.5 4324.1 12418.2
Zn 611.3 720.9 897.6 13515.4 4328.0 12225.0
Free ligand 659.6 739.9 966.7 13772.3 4377.1 12467.2
Dehye units. As may he seen, upon going from Mn to Fe the electric dipole moment increases, while from Fe to Co it decreases, from Co to Cu - increases again and from Cu to Zn - decreases again. The large values of dipoles for the complexes indicated are perfectly understandahle hecause, as it may he seen on Figures 1 - 6, all they are distinctly asymmetric. It is extremely interesting that the electric dipole moment reaches the maximal value in the Fe11 complex, for which, judging hy values of valence angles and bonds lengths (Table 2), this asymmetry must he less pronounced. Also, it is interesting that the character of change of electric dipole moment values for these complexes in the Mn-Zn series is reverse in comparison with the character of change of values of M-N hond lengths (see ahove).
Conclusions
As may be seen from the aforesaid, all macrotricyclic M11 complexes with 4,6,6-trimethyl-2,3,7,8-tetraazanonen-3-dithiohydrazide-1,9 considered here have quasi-tetrahedral coordination of the four nitrogen donor atoms to the central M11 ion. Significantly, the values of sum of valence angles Z(N1)(M1)(N2), Z(N2)(M1)(N6), Z(N6)(M1)(N5) and Z(N5)(M1)(N1) formed by the corresponding metal with two neighboring nitrogen atoms, surpass 360° for all M11 ions considered here. At the same time, the sum of non-valence angles Z(N1)(N2)(N6), Z(N2)(N6)(N5), Z(N6)(N5)(N1) and Z(N5)(N1)(N2), as a rule, is considerably smaller than 360° (in the case of Zn - even smaller than 300o), which is
additional evidence of quasi-tetrahedral orientation of donor centers of the polyamine ligand around M". The character of change of M-N bond lengths in the Mn-Zn series, altogether, coincides with character of change of radii of divalent ions in the same series; nevertheless, the N-N bond lengths in all these complexes are practically equal. Minimal values of M-N bond lengths are reached in the case of the NiII complex, with maximal ones in the case of MnII. All these complexes are strongly asymmetric and have no elements of symmetry; this fact is in full agreement with the large values of their electric dipole moment (3.7 - 6.3 Debye units). These and similar data are of certain interest for structural coordination chemistry of macrocyclic complexes, especially as experimental determination of molecular structures of compounds considered in this paper is so far extremely difficult.
Acknowledgements. The Russian Foundation for Basic Research (RFBR) is acknowledged for financial support of this work (grant N 09-03-97001). Also, authors are grateful to the Supercomputer Center of Kazan Scientific Center of Russian Academy of Sciences, where all quantum-chemical calculations were carried out.
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Received 20.02.2010 Accepted 19.05.2010 First published on the web 08.09.2010
