Formation of H-bonding networks in the solid state structure of a trinuclear cobalt(iii/ii/iii) complex with N2O2 donor Schiff base ligand and glutaric acid as bridging co-ligand: synthesis, structure and DFT study

A trinuclear linear mixed-valence centrosymmetric cobalt(iii)-cobalt(ii)-cobalt(iii) complex, [CoII{(μ-L)(μ-Hglu)CoIII(OH2)}2](ClO4)2·6H2O has been synthesized during tetradentate N2O2 donor 'Schiff base' ligand, H2L {N,N'-bis(salicylidene)-1,3-diaminopropane} and glutaric acid (H2glu) as anionic co-ligand. The complex has been characterized by spectroscopic measurements and its solid state structure has been determined by single crystal X-ray diffraction analysis. The supra-molecular assembly formed by the hydrogen bonding interactions in the solid state of the complex has been analysed using DFT calculations.

Application of a distinctly bent, trinuclear, end-to-end azide bridged, mixed valence cobalt(iii/ii/iii) complex in the fabrication of photosensitive Schottky barrier diodes

A mixed-valence trinuclear cobalt(iii)-cobalt(ii)-cobalt(iii) complex, [(μ-1,3-N3)Co3L(N3)3]·MeOH has been synthesized using a tetradentate N2O2 donor 'reduced Schiff base' ligand, H2L {1,3-bis(2-hydroxybenzylamino)2,2-dimethylpropane} and azide as anionic co-ligand. The complex has been characterised by elemental analysis, IR, UV-vis spectroscopy and single-crystal X-ray diffraction studies etc. The cobalt(iii)-cobalt(ii)-cobalt(iii) skeleton in the complex is non-linear and non-centrosymmetric. The redox behavior of the complex was studied by using Cyclic Voltammetry (CV). The complex is found to be a semiconductor material as confirmed by determining the band gap of this complex by experimental as well as theoretical studies. The band gap in the solid state has been determined experimentally. The conductivity of the synthesized complex based device improves considerably in illumination conditions from the non-illuminated conditions. The complex has also been used to fabricate Schottky barrier diodes.

Structure-directing role of CH⋯X (X = C, N, S, Cl) interactions in three ionic cobalt complexes: X-ray investigation and DFT study using QTAIM Vr predictor to eliminate the effect of pure Coulombic forces

Three cobalt complexes, namely [CoIII(HL1)2(N3)2]ClO4 (1), [CoIII(L2)(HL2)(N3)]ClO4·1.5H2O (2), and [CoIII(L3)(HL3)(NCS)]2 [CoIICl2(NCS)2] (3), where HL1 = 2-(3-(dimethylamino)propyliminomethyl)-6-methoxyphenol, HL2 = 2-(2-(dimethylamino)ethyliminomethyl)-4,6-dichlorophenol, and HL3 = 2-(2-(dimethylamino)ethyliminomethyl)-6-methoxyphenol, as potential tridentate N2O-donor Schiff base ligands, were synthesized and characterized using elemental analysis, IR and UV-vis spectroscopy, and single-crystal X-ray diffraction studies. All three were found to be monomeric ionic complexes. Complex 1 crystallizes in the orthorhombic space group Pbcn, whereas both complexes 2 and 3 crystallize in triclinic space groups, P1̄. Further, 1 and 2 are cationic complexes of octahedral cobalt(iii) with perchlorate anions, whereas complex 3 contains a cationic part of octahedral cobalt(iii) and an anionic part of tetrahedral cobalt(ii). Hydrogen-bonding interactions involving aromatic and aliphatic CH bonds as H-bond donors and the pseudo-halide co-ligands as H-bond acceptors were established, which are important aspects governing the X-ray packing. These interactions were analyzed theoretically using the quantum theory of atoms in molecules (QTAIM) and non-covalent interaction plot (NCI plot) analyses. Moreover, energy decomposition analysis (EDA) was performed to analyze the stabilization of the complexes in terms of the electrostatic, dispersion, and correlation forces.

Insight into charge transportation in cadmium based semiconducting organic-inorganic hybrid materials and their application in the fabrication of photosensitive Schottky devices

A coordination polymer (1) and a trinuclear complex (2) have been synthesized using a compartmental N₂O₂O₂' donor Schiff base ligand. Both complexes are characterized using different spectroscopic techniques and their structures are determined using single crystal X-ray diffraction analyses. Energies associated with different non-covalent (S⋯O chalcogen bonds, C-H⋯H-C, C-H⋯I and C-H⋯π) interactions in the solid state of both complexes have been calculated using the Turbomole program. Investigations of electrical conductivity and photosensitivity of both complexes reveal that suitable Schottky diode devices could be fabricated from both complexes. The current vs. voltage plots of the complex based devices have been used to calculate the conductivity under dark and irradiation conditions. In both complexes the charge transportation mainly occurs through space which involves the hopping process. Standard band theory has been used to compare the experimental and theoretical results of optoelectronic measurements. The calculations confirm that both are direct band gap (2.78 and 3.30 eV) semiconductors and that complex 1 exhibits a lower band gap, in line with the experimental results (3.21 and 3.43 eV in 1 and 2, respectively).

Synthesis and crystal structures of two tri- and tetra-heterometallic Ni(ii)–Mn(ii)/Ni(ii)–Co(iii) complexes from two different Ni(ii)-containing metalloligands: effective catalytic oxidase activity and Schottky device approach

The development of tri- and tetra-nuclear heterometallic Ni(ii)–Mn(ii)/Ni(ii)–Co(iii) complexes with effective catalytic oxidase activity and the Schottky device approach.

Synthesis, Characterization, and Catalytic Study of Amine-Bridged Bis(phenolato) Co(II) and Co(II/III)-M(I) Complexes (M = K or Na)

Co(II) complexes 1-3 bearing amine-bridged bis(phenolato) complexes have been synthesized through reactions of bis(phenols) with CoCl₂ or Co(OAc)₂. Oxidation of the Co(II) complex with air resulted in partial oxidation, generating mixed valence Co(II/III) complexes 4 and 5. In addition, due to the presence of alkali compounds (KOAc and NaOMe), 4 and 5 formed as Co-alkali metal heterometallic complexes, which are the first example of mixed valence Co(II/III)-M(I) (M = K or Na) complexes. Complexes 1-5 showed good activity in the cycloaddition of epoxides and CO₂ under atmospheric pressure, generating cyclic carbonates in 40-99% yields. Co(II/III)-Na(I) complex 5 performed better in reactions of bulkier substrates, underlining the enhanced activity of mixed valence Co-alkali metal heterometallic complexes. On the contrary, complex 5 showed limited activity in copolymerization of epoxide and CO₂.

Phenoxo-bridged dinuclear mixed valence cobalt(III/II) complexes with reduced Schiff base ligands: synthesis, characterization, band gap measurements and fabrication of Schottky barrier diodes

Two homometallic class-I dinuclear mixed valence cobalt complexes, [(N3)CoIIIL1(μ-C6H4(NO2)CO2)CoII(N3)] (1) and [(N3)CoIIIL2(μ-C6H4(NO2)CO2)CoII(N3)] (2), have been synthesized using multisite N2O4 coordination ligands, H2L1 {where H2L1 = (2,2-dimethyl-1,3-propanediyl)bis(iminomethylene)bis(6-methoxyphenol) and H2L2 = (2,2-dimethyl-1,3-propanediyl)bis(iminomethylene)bis(6-ethoxyphenol)}. Each complex has been structurally characterized by single crystal X-ray diffraction and spectral analysis. Both the cobalt centers in these dinuclear complexes adopt a distorted-octahedral geometry, where the cobalt(iii) center resides at the inner N2O2 cavity and the cobalt(ii) center resides at the outer O4 cavity of the reduced Schiff base. Both of them show good electrical conductivity, which has been rationalized by band gap measurements. The band gap in the solid state has been determined by experimental and DFT calculations and it confirms that each of the two complexes behaves as a semiconductor. The space-charge-limited current (SCLC) theory is employed to evaluate the charge transport parameters such as effective carrier mobility and transit time for both complexes. The difference in the conductivity values of the complexes may be correlated with the strengths of extended supramolecular interactions in the complexes. Bader's quantum theory of atoms-in-molecules (QTAIM) is applied extensively to get quantitative and qualitative insights into the physical nature of weak non-covalent interactions. In addition, the non-covalent interaction reduced density gradient (NCI-RDG) methods well support the presence of such non-covalent intermolecular interactions.

Insight into non-covalent interactions in two triamine-based mononuclear iron(iii) Schiff base complexes with special emphasis on the formation of Br⋯π halogen bonding

The nature and characteristics of noncovalent interactions that play important roles in the crystal packing of two iron(iii) complexes have been discussed.

Differentiating intramolecular spodium bonds from coordination bonds in two polynuclear zinc(ii) Schiff base complexes

Two new zinc(ii) complexes have been synthesized and characterized. Theoretical study is devoted to distinguish between conventional coordination bonds and spodium bonds between the zinc and oxygen centers.

Synthesis, characterization, self-assembly and non-ohmic Schottky barrier diode behaviors of two iron(iii) based semiconductors with theoretical insight

Schottky barrier diodes have been fabricated using two iron(iii) Schiff base complexes. The total and partial DOS values have been calculated using DFT to calculate the band gaps in these complexes.

Methylene spacer regulated variation in supramolecular assembly of zinc(ii) dicyanamide complexes with reduced Schiff base ligands: synthesis, structure and DFT study

Three tetranuclear zinc dicyanamide complexes with three potential hexadentate reduced Schiff base ligands have been synthesized and characterized. The DFT study is devoted to the analysis of the competition between C–H⋯π and π⋯π interactions.

A theoretical insight into non-covalent supramolecular interactions in the solid state structures of two octahedral iron(iii) complexes

The nature and characteristics of the C–H⋯π interactions that play an important role in crystal packing of two iron(iii) complexes have been discussed. The DFT calculations have been conducted to determine the interaction energies in these complexes.