Synthesis, characterization, crystal structure and predicting the second-order optical nonlinearity of a new dicobalt(III) complex with Schiff base ligand

Electronic structures, bonding aspects and spectroscopic parameters of homo/hetero valent bridged dinuclear transition metal complexes

Bridged dinuclear metal complexes have fascinated scientists worldwide, and remarkable success has been achieved to unravel the electronic structures, structure-function relationship, coordination environments, and fine mechanistic details of the enzymes owing to the repercussion of biomimetic studies carried out on dinuclear model systems. Molecular level study of these systems integrated with spectroscopic study helps in gaining deep insights about structural and electronic aspects of natural enzymatic systems. Considering the same, here first time we report DFT study on bridged non-heme metal complexes based on N-Et-HPTB ligand system containing homovalent (M^IIM^II); {[(Mn^II)₂(O₂CCH₃)(N-Et-HPTB)]²⁺; Species I), [(Fe^II)₂(O₂CCH₃)(N-Et-HPTB)]²⁺; Species II), [(Co^II)₂(O₂CCH₃)(N-Et-HPTB)]²⁺; Species III)} and heterovalent (M^IIIM^II): {[(Mn^III)(Mn^II)(O₂)(N-Et-HPTB)]²⁺; Species Ia) [(Fe^III)(Fe^II)(O₂)(N-Et-HPTB)]²⁺; Species IIa) and [(Co^III)(Co^II)(O₂)(N-Et-HPTB)]²⁺; Species IIIa)} dinuclear metal centres. Bridging oxygen bears a significant spin density which may prompt important chemical reactions involving activation of bonds like C-H/O-H/N-H etc. TD-DFT calculations for UV-Visible absorption have been carried out to further shed light on structural-functional and electronic structures of these dinuclear species. Studying these dinuclear species may be a good starting point for the study of active sites of the bimetallic centre of dinuclear enzymes and thus may serve as fascinating spectroscopic models. Further, FMO analysis, MEP mapping, and NBO calculations were employed to analyze bonding aspects predict theoretical reactivity behaviour and any kind of stabilizing interactions present in the reported species.

A mononuclear cobalt(II) salophen-type complex: Synthesis, theoretical and experimental electronic absorption and infrared spectra, crystal structure, and predicting of second- and third-order nonlinear optical properties

A tetradentate Schiff base ligand, (4-nitro-N,N'-o-phenylene-bis(5-methoxysalicylideneimine)) (H₂L), and its cobalt(II) complex (CoL•DMF) were synthesized. Elemental analysis, and FT-IR and ¹H NMR spectra were used to confirm the molecular structure of H₂L ligand. In addition, elemental analysis, molar conductance measurement, infrared and electronic absorption spectroscopies as well as single crystal X-ray diffraction were employed to distinguish the molecular structure of the complex that has a slightly distorted square-planar geometry around the cobalt(II) ion. The geometries of H₂L and CoL were optimized by means of the DFT/(U)PBE0/Def2-TZVP level of theory. Good agreement of the optimized geometric parameters of the complex with the corresponding experimental ones and successfully reproduction of the FT-IR spectra of the ligand and complex validated the applied method. Based on the optimized structure of CoL, its electronic absorption spectrum was reproduced by using time-dependent density functional theory (TDDFT) at the same level. Its analysis was carried out to assign the observed electronic transitions and determine their characters. The computed nonlinear optical (NLO) parameters (β, γ and < γ > values) of H₂L and CoL by using TDDFT at the same level combined with the sum-over-states (SOS) method are considerable larger values than reference compound i.e. urea. The ligand and the complex in the absence of nitro and methoxy moieties referred to as H₂L' and CoL' respectively were optimized to elucidate the effect of these moieties on hyperpolarizabilities values.

Packing polymorphism in the structure of trans-aqua-[N,N'-bis-(salicyl-idene)ethane-1,2-di-amine-κ4 O,N,N',O']chlorido-manganese(III) monohydrate

The crystal structure of the title complex (systematic name: trans-aqua-chlorido-{2,2'[ethane-1,2-diylbis(nitrilo-methyl-idyne)]diphenolato-κ4 O,N,N',O'}manganese(III) monohydrate), [Mn(C16H14N2O2)Cl(H2O)]·H2O has been reported previously in the space group P21/n [Panja et al. (2003 ▸). Polyhedron, 22, 1191-1198]. We obtained the same hydrated complex through an alternative synthesis, and crystallized a new polymorph, in the space group P21. The mol-ecular conformation of the complex is virtually unmodified, but the absence of the glide plane in the new polymorph halves the unit-cell parameter c, affording a non-centrosymmetric crystal structure with Z = 2, while the previously reported crystal is centrosymmetric with Z = 4. Both phases represent a case of packing polymorphism, similar to other dimorphic crystal structures retrieved from the Cambridge Structural Database.

Crystal structure and Hirshfeld surface analysis of (E)-N'-benzyl-idene-4-chloro-benzene-sulfono-hydrazide and of its (E)-4-chloro-N'-(ortho- and para-methyl-benzyl-idene)benzene-sulfono-hydrazide derivatives

(E)-N'-Benzyl-idene-4-chloro-benzene-sulfono-hydrazide, C13H11ClN2O2S, (I), and its ortho- and para-methyl-substituted derivatives, C14H13ClN2O2S, namely (E)-4-chloro-N'-(2-methyl-benzyl-idene)benzene-sulfono-hydrazide, (II), and (E)-4-chloro-N'-(4-methyl-benzyl-idene)benzene-sulfono-hydrazide, (III), have been synthesized, characterized spectroscopically and their crystal structures determined to investigate the effect of the substitution site of the benzyl-idene group on the structural and supra-molecular features in these compounds. Compounds (I) and (II) are isotypic while compound (III) is different. All three mol-ecules are bent at the S atom with C-S-N-N torsion angles of -66.0 (3), -66.0 (3) and -58.4 (2)° for (I), (II) and (III), respectively. The hydrazone portions of the mol-ecules, S-N-N=C, are slightly twisted from planarity, with a torsion angle of 166.5 (3)° in (I), 165.4 (3)° in (II) and 157.9 (2)° in (III). The two aromatic rings present in the compounds are inclined to each other by 78.4 (2), 74.8 (2) and 76.9 (1)° in (I), (II) and (III), respectively. In the crystal structure of the parent compound (I), and of the ortho-methyl derivative (II), an N-H⋯O hydrogen bond links the mol-ecules into chains along [001], which are inter-connected by weak inter-molecular C-H⋯O inter-actions, generating layers lying parallel to the bc plane. In the crystal of the para derivative (III), however, the packing is significantly different. Here mol-ecules are linked by pairs of N-H⋯O hydrogen bonds, forming inversion dimers with an R 2 2(8) ring motif. The dimers are then linked by C-Cl⋯π inter-actions, forming ribbons propagating along [10]. Hirshfeld surface analyses show that the van der Waals inter-actions constitute the major contribution to the inter-molecular inter-actions in the crystal structures of all three compounds. The fingerprint plots indicate that the H⋯H contacts make the largest contributions to the Hirshfeld surfaces.

A Binuclear Copper(II) Complex with Diphenoxido-bridges: Synthesis, Characterisation, Crystal Structure and Predicting the Magnetic Coupling Constant

Reaction of copper(II) acetate with 1,1′-[(2,2-dimethylpropane-1,3-diyl)bis(nitrilomethylidyne)]-di-2-naphthol (H2L) gave the diphenoxido-bridged binuclear copper(II) complex [Cu2L2]. Its crystal structure shows a slightly distorted square pyramidal geometry around both of the copper(II) ions. In the symmetric Cu2O2 core, each of the phenoxido bridges occupies an equatorial position around one of the copper(II) centres. A broken symmetry (BS) computation based on density functional theory (DFT) evaluated the magnetic interaction in the complex using the (U)B3LYP level of theory in association with the basis sets LANL2DZ for the copper atoms and 6-31G** for the other atoms. The calculations showed ferromagnetic interaction between the two magnetic copper(II) centres with a magnetic coupling constant (J) of 1.16 cm−1.