Molecular orbital calculations on transition metal complexes

INDO SCF MO calculations are reported for the complexes (C₅H₅)M(C₇H₇) (M = Ti, V and Cr), and for the corresponding V and Cr cations. The results correctly predict¹ A ₁ ground states for the V⁺ and the neutral Ti and Cr species, and for the neutral V and Cr⁺ complexes confirm the² A ₁ ground levels. The formally metald-levels followed theH ^core sequencee ₂<a ₁<e ₁, and the most important interactions were those between the metale ₂ level and the ligand C₇H₇ -orbitals, and between the metale ₁ level and the ligand C₅H₅ -orbitals. Calculations also satisfactorily reproduced other experimental quantities, and the results indicate that thee ₂ ligand interaction becomes more important, and thee ₁ ligand interaction less important, with increasing size of the ligand ring.     

Solvent effect on pyridine derivatives. Molecular iodine donor-acceptor equilibria. The isoquinoline-I2-organic solvent system and the 2,4-lutidine-I2-organic solvent system

The absorption spectra of isoquinoline-iodine or 2,4-lutidine-iodine solutions in organic solventsn-hexane,n-heptane, cyclohexane, carbon tetrachloride, benzene, toluene, chlorobenzene, ando-dichlorobenzene have been measured and interpreted in terms of the D+I₂=DI₂ equilibrium, where D is isoquinoline or 2,4-lutidine. Values ofK (288–320°K), ΔH^o, and ΔS^o for the reaction were calculated. A correlation between theK values and the solubility parameter of the solvent (Buchowski's relation) has been found.     

芳基四硫富瓦烯与碘电荷转移复合物的合成及其晶体结构

采用缓慢挥发溶剂的方法合成了硫原子桥联芳基取代四硫富瓦烯（Ar-S-TTF）与碘的3种电荷转移复合物（1^+·）（I₃）·I₂、（2^+·）（I₅）·I₂和（3²⁺）（I₃）₂,采用单晶X射线衍射、紫外可见光谱、循环伏安对其进行了表征。复合物（1^+·）（I₃）·I₂为C2/c空间群,1^+·呈椅式构型。化合物1与碘之间在溶液中和复合物中电荷转移一致。复合物（2^+·）（I₅）·I₂为P1空间群,2^+·呈椅式构型。复合物（3²⁺）（I₃）₂为Pbca空间群,3²⁺呈独特的平面构型。化合物2和3与碘之间在溶液中和复合物中呈现不同的电荷转移。复合物中聚碘阴离子呈现不同的堆积结构：由I₃^-或I₅^-/I₂组成的一维链状和I₃^-/I₂组成的二维网格状。     

芳基四硫富瓦烯与碘电荷转移复合物的合成及其晶体结构

采用缓慢挥发溶剂的方法合成了硫原子桥联芳基取代四硫富瓦烯(Ar-S-TTF)与碘的3种电荷转移复合物(1^+·)(I₃)·I₂、(2^+·)(I₅)·I₂和(3²⁺)(I₃)₂,采用单晶X射线衍射、紫外可见光谱、循环伏安对其进行了表征。复合物(1^+·)(I₃)·I₂为C2/c空间群,1^+·呈椅式构型。化合物1与碘之间在溶液中和复合物中电荷转移一致。复合物(2^+·)(I₅)·I₂为P1空间群,2^+·呈椅式构型。复合物(3²⁺)(I₃)₂为Pbca空间群,3²⁺呈独特的平面构型。化合物2和3与碘之间在溶液中和复合物中呈现不同的电荷转移。复合物中聚碘阴离子呈现不同的堆积结构：由I₃^-或I₅^-/I₂组成的一维链状和I₃^-/I₂组成的二维网格状。     

Solvent effect on CuCl2-pyridine derivative complexes: UV-VIS and E.S.R. study of the CuCl2-2,4-dimethylpyridine-solvent systems

Summary The electronic (400–800 nm; 298.2 K) and E.S.R. spectra (298 K; 77 K) have been measured for CuCl₂-2,4-dimethylpyridine(2,4-Me ₂ py)-solvent systems (solvents: aliphatic and aromatic hydrocarbons, carbon tetrachloride, chloroform, 1,1,2,2-tetrachloroethane). In all the media CuCl₂ forms electrically neutral strongly distorted six-coordinated complexes, the extent of tetragonality being greater than for analogous complexes with non-a-substituted pyridines. In contrast to aliphatic and aromatic hydrocarbons protic solvents and, unexpectedly, aprotic carbon tetrachloride solvate the CuCl₂-Me ₂ py complex comparatively strongly, most probably through interactions with the chlorine ligand. The results for 2,4-Me ₂ py were compared with those for pyridine, 4-ethylpyridine and isoquinoline and discussed in terms of steric effects on solvation. In particular,a-substitution seems to hinder the solvation of the complex by the amine.

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Lösungsmitteleinfluß auf den Koordinationszustand des CuCl₂ in Lösungen. Elektronen- und EPR-Spektren der CuCl₂-2,4-Dimethylpyridin-nichtwäßrigen Lösungsmittel-Systeme

Zusammenfassung Es wurden die Absorptions-Elektronenspektren (400–800 nm; 298.2 K) und EPR-Spektren (298 K; 77 K) verschiedener CuCl₂-2,4-Dimethylpyridin(2,4-Me ₂ py)-Lösungsmittel(L)-Systeme gemessen und mit analogen CuCl₂-Pyridinbasen-L-Systemen verglichen (L=aliphatische und aromatische Kohlenwasserstoffe, Chloroform, Tetrachloromethan, 1,1,2,2-Tetrachlorethylen). In allen Lösungen bildet CuCl₂ mit Pyridinbasen neutrale, stark verzerrt oktaedrische monomere Komplexe. Die Verzerrung nimmt mita-Substitution zu. Bemerkenswert ist, daß CCl₄ einen Mediumeffekt zeigt, der demjenigen der protischen Lösungsmitteln ähnlich ist; er solvatiert die Komplexe verhältnismäßig stark, möglicherweise an den Chloridliganden. Die Komplexe vona-substituierten Phyridinbasen sind gegenüber Solvatation weniger empfindlich als die übrigen.

     

Synthesis,and characterization of some Cu(I) complexes having propionitrile and pyridine moieties: An investigation on their antibacterial properties

The aim of producing new biologically active compounds lead to the synthesis of some Cu(I) complexes of general formula [Cu(C₂H₅CN)₄][A] and [Cu(C₅H₅N)₄][A] (1–4) {where A: counter anion = B(C₆F₅)₄⁻ and B{C₆H₃(m-CF₃)₂}₄⁻} from the reaction of CuCl and silver salt of the corresponding counter anion. The complexes were characterized using elemental analysis, ¹H NMR, ¹¹B NMR, FT-IR Spectroscopy, UV–visible spectroscopy and thermo-gravimetric analysis (TGA). The antibacterial activities of all complexes are evaluated by the minimal inhibitory concentration (MIC), using the micro-broth dilution method, against eight bacteria (Gram-negative and Gram-positive), each with fresh clinical isolates. The MIC results were compared with those of Oxytetracycline agent as a positive control. In most cases, the compounds show broad-spectrum activities that were either, more active, or equipotent to, the antibiotic agent in the comparison tests. Complex 4 showed the greatest activity against Proteus mirabilis (Gram- negative) with a minimum inhibitory concentration (MIC) of 8 µg/mL, while complexes 2 and 3 showed the lowest activity against Pseudomonas aeruginosa (Gram-negative) and against Staphylococcus aureus (Gram-positive) with a concentration of 512 µg/mL.     

Calorimetric investigations of the solvent effect on complex formation between pyridine derivatives and molecular iodine

The heats of solution of isoquinoline and 2,4-lutidine and heats of 11 complex formation with molecular iodine inn-hexane, cyclohexane, CCl₄, benzene, and chlorobenzene have been determined by the calorimetric method. The heats of transfer of the donor and donor-acceptor complex from nonsolvating medium (n-hexane) to the particular solvent were calculated and discussed in terms of donor and solvent properties and solute-solute-solvent interactions.Presented at the IV International Symposium on Solute-Solute-Solvent Interactions, Vienna, September 11–16, 1978, pp. 152–154.     

Synthesis, characterization and fluorescence properties of novel pyridine dicarboxylic acid derivatives and corresponding Tb(III) complexes

Two novel ligands containing two pyridine-2,6-dicarboxylic acid conjugative units, 4-(2-(2,6-dicarbox-ypyridin-4-yl)vinyl)pyridine-2,6-dicarboxylic acid (L(1)) and 4-(4-(2-(2,6-dicarboxypyridin-4-yl)vinyl)styryl)pyridine-2,6-dicarboxylic acid (L(2)) and their complexes with Tb(III) have been synthesized and characterized by elemental analysis, IR spectra and NMR. The ligand synthetic route was optimized and the yield of ligands reached over 78% as a result of the Wittig-Horner reaction used. The fluorescent intensities of these complexes with corresponding complexes with single pyridine-2,6-dicarboxylic acid unit was compared. The result has shown that the ligands with two pyridine-2,6-dicarboxylic acid units are the excellent sensitizers to lanthanide fluorescence. Also, we investigated the fluorescence properties of these complexes in different solution and in different pH value. Due to their excellent green-emmiter, they would be a potential candidate material for applications in organic light-emitting devices and medical diagnosis.     

Theoretical study for quercetin/β-cyclodextrin complexes: quantum chemical calculations based on the PM3 and ONIOM2 method

The inclusion interaction between quercetin and β-cyclodextrin (β-CD) binding site has been investigated, based on PM3 and ONIOM2 methods. The obtained results clearly indicate that the orientation in which the B ring of the guest molecule located near the secondary hydroxyls of the β-CD cavity is preferred in the binding energy. Moreover, Analyses regarding the complex structures suggest that one hydrogen bond between 7-hydroxy group (OH) of quercetin and 6-OH of β-CD is formed. This hydrogen bond interaction plays an important role in the bound quercetin/β-CD complex.     

Cyclometalated iridium(III) complexes containing 2-phenyl-2H-indazole ligand: Synthesis,photophysical studies,and DFT calculations

Heteroleptic cyclometalated iridium(III) complexes ( Ir1 – Ir5 ) featuring piz-based ligands and acetylacetone ancillary ligand are synthesized and characterized. Their photophysical and electrochemical properties were studied, and DFT calculations were used to further support the experiment results. All the complexes emit yellow color with quantum yields of 12.2–56.5% in dichloromethane solution at room temperature, and the emission originates from a hybrid ³MLCT/³ILCT/³LLCT excited state.     

Iodine binding by amylopectin and stability of the amylopectin–iodine complex

The iodine binding capacity (IBC) of amylopectin (AP, from potatoes) is determined to be around 0.38% (w/w) of the total AP in the solution. The mass of iodine bound comprises about 13.6% of the mass of AP involved with the complex, suggesting that with every four iodine atoms bound there are 23 anhydroglucose residues (AGU). Since our previous study indicates that four iodine atoms within the helix of 11 AGUs form a chromophore unit in the API complex, only 48% of the AGUs (11 out of 23) in the AP molecule are directly involved with the iodine. The heat of reaction for the API complex formation is determined to be around ?47 kJ/mol of I–I units bound and is significantly lower in magnitude than that of the amylose-iodine (AI) complex [Biopolymers, 31 , 57 (1991)]. A possible mechanism has been proposed for the formation of AI and API complexes with fixed compositions. © 1994 John Wiley & Sons, Inc.     

Molecular orbital calculations on transition metal complexes : XX. The π-cyclopentadienyl-π-benzene complexes of chromium and manganese

INDO SCF MO calculations are reported for the complexes (C₅H₅)M(C₆H₆) (M = Cr and Mn) and for the corresponding cations. A ²A₁ ground state is correctly predicted for the neutral Cr system, and other experimental quantities are satisfactorily reproduced. The dominantly metal d-levels yield the H^core sequence e₂ < a₁ < _e1 and the principal interactions were found to be those between the metal e₁ level and the π-orbitals of the C₅H₅ ligand, and between the metal e₂ level and the ligand C₆H₆ π-orbitals. From the state energies of the formally 3d⁵ species estimates were made of the one-electron 3d splittings in the ligand field model, and comparisons made with similar results for M(C₅H₅)₂, M(C₆H₆)₂, and (C₅H₅)M(C₇H₇) systems: these indicated the general validity of the bonding scheme in which the extent of the metal—ligand interaction via the e₁ and e₂ 3d levels varied systematically with the sizes of the ligand rings.     

Studies on the mixed-ligand complexes of copper(II) with gallic acid and pyridine carboxylic acids and their benzologues

Summary The ternary complex formation of copper(II) with gallic acid (gal) and 2-hydroxy nicotinic acid (hyna), 2-mercapto nicotinic acid (mena), salicylic acid (sa) or thiosalicylic acid (tsa) as a second ligand in a 1:1:1 molar ratio has been investigated in 40% (v/v) ethanol using spectrophotometric andpH titration methods. The solution equilibria of the ternary systems have been determined and the stability constants of the mixed complexes has been evaluated. Considering all parameters, the Cu-gal-sa ternary system was proved as a suitable, rapid, and sensitive spectrophotometric indicator for determining traces of copper.The ternary system containingsa obeysBeer's law up to 3.4 µg·ml^–1 copper. The optimum range for the determination of copper (Ringbom) atpH 6.0 ranges from 0.63 to 1.74 µg·ml^–1 of copper. The molar absorptivity of the ternary complex is 1.3×10⁴l·mol^–1·cm^–1.

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Untersuchungen anmixed-ligand — Komplexen von Kupfer(II) mit 3,4,5-Trihydroxybenzoesäure und Pyridincarbonsäuren und ihren C-Homologen

Zusammenfassung Die Bildung ternärer Komplexe von Kupfer(II) mit 3,4,5-Trihydroxybenzoesäure (gal) und 2-Hydroxynicotinsäure (hyna), 2-Mercaptonicotinsäure (mena), Salicylsäure (sa) oder Thiosalicylsäure (tsa) in einem molaren Verhältnis von 1:1:1 wurde mittels spektrophotometrischer und potentiometrischer Methoden in 40% (v/v) Ethanol untersucht. Die Lösungsgleichgewichte der termären Systeme und die Stabilitätskonstanten der gemischten Komplexe wurden bestimmt. Unter Berücksichtigung aller Parameter erwies sich das termäre System Cu-gal-sa als geeigneter schneller und empfindlicher Indikator zur Spurenanalyse von Kupfer.Dassa enthaltende ternäre System gehorcht demBeerschen Gesetz bis zu einer Kupferkonzentration von 3.4 µg·ml^–1. Der optimale Bereich zur Bestimmung von Kupfer (Ringbom) beipH 6.0 erstreckt sich von 0.63 bis 1.74 µg Cu pro ml. Die molare Extinktion des ternären Komplexes beträgt 1.3×10⁴l·mol·cm^–1.

     

Molecular orbital calculations on the conformation of polypeptides and proteins

Quantum mechanical calculations using the PCILO method have been performed on the tripeptide model CH₃CO-X-Y-NHCH₃. Competition between C₅, C₇, C₁₀ rings and open structures has been investigated through mapping of the whole {φ, Ψ} conformational space and energy minimization. From these results, it appears that the C₁₀ ring simulating the folding named U-turn, involving a hydrogen bond between the i...i + 3 residues, is the most probable structure although not the most stable in energy. The results are used for predicting the frequency of U-turns in proteins, α-chymotrypsin is given as an example.     

Copper(II) complexes of 2-amino-5-chloro-3-fluoropyridine: syntheses and magnetic properties of (3,5-FCAP)2CuX2 and (3,5-FCAPH)2CuX4

Using 2-amino-5-chloro-3-fluoropyridine, two new copper halide coordination complexes and two new salts have been synthesized: [(3,5-FCAP)₂CuCl₂] (1), [(3,5-FCAP)₂CuBr₂](2), (3,5-FCAPH)₂[CuCl₄] (3) and (3,5-FCAPH)₂[CuBr₄] (4) [3,5-FCAP?=?2-amino-5-chloro-3-fluoropyridine; 3,5-FCAPH?=?2-amino-5-chloro-3-fluoropyridinium]. These complexes have been analyzed through single-crystal X-ray diffraction and temperature-dependent magnetic susceptibility. Compounds 1 and 2 crystallize in the triclinic space group P-1, while 3 and 4 crystallize in the monoclinic space group P2₁/c. All structures were distinct, with 1 giving a bihalide bridged chain, 2 yielding a halide bridged dimer, 3 forming a two-halide bridged chain via short Cl???Cl contacts, and 4 producing a rectangular sheet via short Br???Br contacts. All four compounds exhibit anti-ferromagnetic interactions and were fit to linear chain (1 and 3), dimer (2), and rectangular 2-D sheet (4) models. The resulting J/k_B values are ?3.4(1), ?31.3(8), ?0.9(1), and ?9.46(6)?K with an α value (α?=?J?/J) of 0.06(2), respectively.     

磷酸二氢铵水溶液构型能删和径向分布函数的分子动力学模拟

采用分子动力学模拟对不同温度下磷酸二氢铵水溶液的构型能和径向分布函数进行了研究．磷酸二氢根被看作七节点模型,铵离子被看作五节点模型,而水分子则被看作简单点电荷模型．在饱和温度附近,体系局域粒子数密度有波动．373-400K的溶液势能增长缓慢表明磷酸二氧铵部分分解．磷酸二氢根中的氧原子与铵离子中氢原子的径向分布函数在三种不同温度下呈现明显不同,表明溶液中平均氢键数目随温度的变化明显改变．温度对磷酸二氢根中的氧原子和氧原子的结合有一定的影响,而在饱和溶液中有更多的生长基无产生．     

Valence basis sets for lanthanide 4f-in-core pseudopotentials adapted for crystal orbital ab initio calculations

Crystal orbital adapted Gaussian (4s4p3d), (5s5p4d) and (6s6p5d) valence primitive basis sets have been derived for calculating periodic bulk materials containing trivalent lanthanide ions modeled with relativistic energy-consistent 4f-in-core lanthanide pseudopotentials of the Stuttgart-Koeln variety. The calibration calculations of crystalline A-type Pm₂O₃ using different segmented contraction schemes (4s4p3d)/[2s2p2d], (4s4p3d)/[3s3p2d], (5s5p4d)/[2s2p2d], (5s5p4d)/[3s3p3d], (5s5p4d)/[4s4p3d], (6s6p5d)/[2s2p2d], (6s6p5d)/[3s3p3d] and (6s6p5d)/[4s4p4d] are discussed at both Hartree–Fock (HF) and density functional theory (DFT) levels for the investigation of basis set size effects. Applications to the geometry optimization of A-type Ln₂O₃ (Ln = La-Pm) show a satisfactory agreement with experimental data using the lanthanide valence basis sets (6s6p5d)/[4s4p4d] and the standard set 6-311G* for oxygen. The corresponding augmented sets (8s7p6d)/[6s5p5d] with additional diffuse functions for describing neutral lanthanide atoms were applied to calculate atomic energies of free lanthanide atoms for the evaluation of cohesive energies for A-Ln₂O₃ within both conventional Kohn-Sham DFT and the a posteriori-HF correlation DFT schemes.     

A new method for partition of interaction energy. Relation between stabilization energy and orbital mixing

A new method for partition of interaction energy is proposed. The scheme given here easily connects the calculated stabilization energy with the orbital mixing in analyzing orbital interactions of molecules. The method can reveal the relation between the change of electron distribution and stabilization energy. As an example, orbital interaction energies are estimated for diazocompounds, diazomethane and diazirine.     

Iodine binding capacity and iodine binding energy of glycogen

The iodine binding capacity (IBC) of glycogen is around 0.30% (w/w) at 3°C. The amount of iodine complexed comprises about 12.5% of the mass of glycogen that takes part in the glycogen–iodine (GI) complex formation. This suggests involvement of four iodine atoms for every 25 anhydroglucose units (AGU, C₆H₁₀O₅). Since the chromophore is due to the I₄ unit within the helix of 11 AGUs, only 44% of the AGUs (11 out of 25) are involved in the complex formation. The heat of formation of the GI complex is around −40 kJ/mol of I₂ bonded. These results suggest remarkable similarities with those of the amylopectin–iodine (API) complex. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1409–1412, 1997