Synthesis, crystal structures, and molecular hyperpolarizabilities of a new Schiff base ligand, and its copper(II), nickel(II), and cobalt(II) metal complexes

Molybdenum Complexes Derived from 2-Hydroxy-5-nitrobenzaldehyde and Benzhydrazide as Potential Oxidation Catalysts and Semiconductors

This study aimed to synthesize molybdenum complexes coordinated with an aroyl hydrazone-type ligand (H2L), which was generated through the condensation of 2-hydroxy-5-nitrobenzaldehyde with benzhydrazide. The synthesis yielded two types of mononuclear complexes, specifically [MoO2(L)(MeOH)] and [MoO2(L)(H2O)], as well as a bipyridine-bridged dinuclear complex, [(MoO2(L))2(4,4'-bpy)]. Those entities were thoroughly characterized using a suite of analytical techniques, including attenuated total reflectance infrared spectroscopy (IR-ATR), elemental analysis (EA), thermogravimetric analysis (TGA), and single-crystal X-ray diffraction (SCXRD). Additionally, solid-state impedance spectroscopy (SS-IS) was employed to investigate the electrical properties of these complexes. The mononuclear complexes were tested as catalysts in the epoxidation of cyclooctene and the oxidation of linalool. Among these, the water-coordinated mononuclear complex, [MoO2(L)(H2O)], demonstrated superior electrical and catalytic properties. A novel contribution of this research lies in establishing a correlation between the electrical properties, structural features, and the catalytic efficiency of the complexes, marking this work as one of the pioneering studies in this area for molybdenum coordination complexes, to the best of our knowledge.

Impedance Spectroscopy as a Powerful Tool for Researching Molybdenum-Based Materials with Schiff Base Hydrazones

Molybdenum coordination complexes are widely applied due to their biological and pharmacological potential, as well as their performance in different catalytic processes. Parent dioxidomolybdenum Schiff base complexes were prepared via the reaction of [MoO₂(acac)₂] with a hydrazone Schiff-base tetradentate ligand. A new hydrazone-Schiff base (H₂L^{1 and 2}) and its corresponding mononuclear and polynuclear dioxidomolybdenum(VI) complex were synthesized and characterized by spectroscopic methods and elemental analyses, and their thermal behavior was investigated by thermogravimetry. The crystal and molecular structures of H₂L² ligands and the complexes [MoO₂(L¹)(H₂O)], [MoO₂(L²)(H₂O)], [MoO₂(L¹)(MeOH)]∙MeOH, [MoO₂(L¹)(EtOH)]∙EtOH, [MoO₂(L¹)(2-PrOH)]∙2-PrOH, and [MoO₂(L¹)]_n were determined by single-crystal X-ray diffraction. Using the in situ impedance spectroscopy method (IS), the structural transformations of chosen complexes were followed, and their electrical properties were examined in a wide range of temperatures and frequencies.

In silico screening of ethyl 4-[(E)-(2-hydroxy-4-methoxyphenyl)methyleneamino]benzoate and some of its derivatives for their NLO activities using DFT

The nonlinear optical (NLO) properties of ethyl 4-[(E)-(2-hydroxy-4-methoxyphenyl)methyleneamino]benzoate (EMAB) and some of its derivatives are investigated herein using the density functional theory (DFT) and time-dependent (TD)-DFT methods. The density functionals B3LYP, CAM-B3LYP, M06-2X and ωB97XD, and basis sets 6-31 + G**, 6-311 + + G** and Def2-TZVPP have been used. From the results, EMAB and its substituted derivatives studied are promising candidates for NLO materials. In all cases, the static first and second hyperpolarizabilities (31.7-86.5 × 10^-30 and 84.4-273 × 10^-36 electrostatic units (esu), respectively) and the frequency-dependent NLO properties are found to be significantly larger (about 43-103 and 28-76 times greater) than those of the NLO prototypical molecule, para-nitroaniline. Furthermore, the maximum absorption wavelengths of the molecules fall within the UV region of the electromagnetic spectrum. Relative to EMAB, the derivatives have shown improved transparency-nonlinearity trade-offs. Natural bond orbital (NBO) and density of states (DOS) analyses herein revealed effective charge transfer within the molecules studied, especially those with stronger electron donors than that in EMAB (methoxy group). Among the molecules studied, the derivative obtained by substituting EMAB's methoxy group with the pyrrolyl group was found to exhibit the best NLO properties. Conclusively, the NLO activities of EMAB can be significantly improved through the substitution of its methoxy group with stronger electron donors.

Origin of Fluorescence from Boranils in the Crystalline Phase

A small series of boranil complexes has been studied by fluorescence spectroscopy. Weakly fluorescent in most organic solvents at room temperature, the target compounds display bright emission in the crystalline phase. X-ray diffraction patterns obtained for single crystals indicate a distorted tetrahedral geometry around the O-B-N center with the boron atom being displaced from the plane of the heterobicyclic ring. Consideration of the various bond lengths in comparison with those of reference compounds indicates that the ancillary phenyl ring, bearing different para-substituents, does not make a prominent contribution to the molecular dipole moment in the solid state. Absorption and fluorescence spectra recorded for the crystals remain remarkably similar to those for liquid solutions and display large Stokes shifts. Proximity broadening is observed in one case. The nitrophenyl derivative exhibits additional absorption and emission bands unique to the solid state and could be indicative of an intermolecular charge-transfer transition. The optical properties are discussed in terms of the crystal packing diagrams.

Representation of a photosensitive Schottky barrier diode made with hetero-dinuclear cobalt(iii)/sodium building blocks

A hetero-dinuclear cobalt(iii)/sodium complex has been synthesized and characterized. The complex which has been used to construct photosensitive Schottky devices, shows interesting C–H⋯π(N₃) interactions in the solid state.

Push–pull unsymmetrical substitution in nickel(ii) complexes with tetradentate N2O2 Schiff base ligands: synthesis, structures and linear–nonlinear optical studies

Push–pull unsymmetrical substitution efficiently modulates the electronic, linear and nonlinear optical properties of nickel(ii) complexes with salen-type ligands.

Visible-light CO2 photoreduction of polyoxometalate-based hybrids with different cobalt clusters

Two novel high-nuclear cobalt-based polyoxometalates can effectively improve photocatalytic activities for CO₂ photoreduction under visible light.

Crystal structure of bis{5-(diethylamino)-2-(((2-oxo-2H-chromen-6-yl)imino)methyl)phenolato-κ2 O,N}cobalt(II), C40H38CoN4O6

C40H38CoN4O6, monoclinic, C2/c (no. 15), a = 25.848(2) Å, b = 9.7537(5) Å, c = 13.8302(11) Å, β = 93.760(7)°, Z = 4, V = 3479.3(4) Å3, R gt(F) = 0.0770, wR ref(F 2) = 0.1824, T = 293 K.

Crystal structure of bis{5-(diethylamino)-2-(((2-oxo-2H-chromen-6-yl)imino)methyl)phenolato-κ2 O,N}copper(II), C40H38CuN4O6

C40H38CuN4O6, monoclinic, P21/c (no. 14), a = 10.590(4) Å, b = 7.273(3) Å, c = 23.345(9) Å, β = 102.347(7)°, Z = 2, V = 1756.5(12) Å3, R gt(F) = 0.0682, wR ref(F 2) = 0.2373, T = 296 K.

Crystal structure of bis{5-methoxy-2-((E)-((4-((E)-1-(methoxyimino)ethyl)phenyl)imino)methyl)phenolato-κ2 N,O)}copper(II), C34H34CuN4O6

C34H34CuN4O6, Monoclinic, P21/c, a = 10.4018(4) Å, b = 6.1634(2) Å, c = 24.2227(15) Å, β = 101.820(5)°, Z = 2, V = 1520.01(13) Å3, R gt(F) = 0.0565, wR ref(F 2) = 0.1455, T = 292 K.

Towards a global greener process: from solvent-less synthesis of molybdenum(vi) ONO Schiff base complexes to catalyzed olefin epoxidation under organic-solvent-free conditions

Schiff base ligands and corresponding molybdenum(vi) complexes, prepared using classical and/or mechanochemical methods, were active as epoxidation pre(catalysts).

A cobalt(ii)heteroarylalkenolate precursor for homogeneous Co3O4 coatings by atomic layer deposition

We present a robust approach to prepare conformal Co₃O₄ nanocoatings on high aspect ratio structures from a new cobalt metalorganic complex.

Copper(II) complexes with imino phenoxide ligands: synthesis, characterization, and their application as catalysts for the ring-opening polymerization of rac-lactide

ABSTRACT

Four new copper complexes based on bidentate imino phenoxide ligands were synthesized and characterized by IR, UV-Vis spectroscopy, ESI mass spectrometry, single crystal X-ray diffraction, and electrochemistry. The crystal structures revealed that the copper(II) atoms are surrounded by phenolate oxygen and imine nitrogen atoms of two ligands in a distorted square-planar geometry. The existence of ligand-centered, as well as Cu(II)-centered quasi-reversible and reversible redox reactions are observed in the cyclic voltammetry experiments of all the complexes. All complexes are able to catalyze the ring-opening polymerization of rac-lactide yielding polymers with moderate molecular weights and moderately broad molecular weight distributions.

GRAPHICAL ABSTRACT

Push-pull effect on the geometrical, optical and charge transfer properties of disubstituted derivatives of mer-tris(4-hydroxy-1,5-naphthyridinato) aluminum (mer-AlND3)

To design innovative and novel optical materials with high mobility, two kinds of disubstituted derivatives for mer-tris(4-hydroxy-1,5-naphthyridinato) aluminum (mer-AlND3) with push (EDG)–pull (EWG) substituents have been designed. The structures of mer-tris(8-EDG-2-EWG-4-hydroxy-1,5-naphthyridinato) aluminum (type I) and mer-tris(8-EWG-2-EDG-4-hydroxy-1,5-naphthyridinato) aluminum (type II) in the ground and first excited states have been optimized at the B3LYP/6-31G(D) and CIS/6-31G(D) level of theory, respectively. It can be seen from frontier molecular orbitals analysis, in all these complexes, the highest occupied molecular orbital (HOMO) is localized on the pyridine-4-ol ring of A-ligand while lowest unoccupied molecular orbital (LUMO) is on the pyridyl ring of B-ligand in ground state irrespective of electron donor/acceptor substitution present on the ligands similar to that of mer-tris(8-hydroxyquinoline) aluminum (mer-Alq3) and parent mer-AlND3.The absorption and emission wavelengths have been evaluated at the TD-PBE0/6-31G(D) level and it can be see that all the type I derivatives show blue shift while most of the type II derivatives show red shift compared to mer-AlND3. All the disubstituted complexes have showed hypsochromic shifts in both the absorption and emission spectra when compared with the calculated absorption and emission spectra respectively of mer-Alq3. It can be seen that the reorganization energies of some of the disubstituted derivatives are comparable with mer-Alq3 and these derivatives might be good candidates for emitting materials in OLED.

Structural, thermal and optical characterization of a Schiff base as a new organic material for nonlinear optical crystals and films with reversible noncentrosymmetry

Macroscopic single crystals of (E)-5-(diethylamino)-2-((3,5-dinitrophenylimino)methyl)phenol (DNP) were obtained from slow cooling of chloroform or dichlorometane saturated solutions at controlled temperature. X-ray diffraction analysis showed that this compound crystallizes in a noncentrosymmetric space group (P2(1)2(1)2(1)). Thermal analysis was performed and indicated that the crystals are stable until 260 °C. Second-order nonlinear optical properties of DNP were experimentally investigated in solution through EFISH technique and in solid state through the Kurtz-Perry powder technique. Crystals of compound DNP exhibited a second-harmonic signals 39 times larger than of the technologically useful potassium dihydrogenphosphate (KDP) under excitation at infrared wavelengths. In addition, the second-order nonlinear optical properties of DNP were also studied at visible wavelengths through the photorefractive effect and applied to demonstrate dynamic holographic reconstruction.

Molecular structures, spectral and computational studies on nicotinohydrazides

The FT-IR and the high resolution (1)H and (13)C NMR spectra have been recorded for N'-(2-methyl-3-phenylallylidene)nicotinohydrazide (1) and N'-(2-methyl-3-phenylallylidene)isonicotinohydrazide (2) and analyzed. (1)H-(1)H COSY spectra were also recorded for the hydrazides. The spectral studies reveal that both the hydrazides exist in the keto form. Theoretical calculations were performed for some possible conformations of the hydrazide and the minimum energy conformers are predicted to be the one in which the azomethine protons are syn to N-NH bond. From the optimized structures, HOMO-LUMO energy gap and geometrical parameters were derived and these parameters were compared with the XRD measurements of hydrazide 1. The vibrational frequencies in the ground state have been calculated using DFT and HF methods and compared with the observed frequencies. Non-linear optical (NLO) behaviour of the hydrazides was investigated by the determination of the electric dipole moment mu, the polarizability alpha and the hyperpolarizability beta using B(3)LYP method.

Bis{1-[3-(diethyl-ammonio)-propyl-imino-meth-yl]naphthalen-2-olato}nickel(II) dinitrate

The asymmetric unit of the title compound, [Ni(C(18)H(24)N(2)O)(2)](NO(3))(2), consists of one half of the centrosymmetric nickel(II) complex cation and a nitrate anion. The Ni(II) atom, lying on an inversion center, is four-coordinated by the phenolate O atoms and imine N atoms of two Schiff base ligands, forming a square-planar geometry. The O- and N-donor atoms are mutually trans. In the crystal structure, the nitrate anions are linked to the complex cations by inter-molecular N-H⋯O hydrogen bonds.

Bis[2-(cyclohexyliminomethyl)-5-methoxyphenolato]copper(II)

In the title centrosymmetric mononuclear complex, [Cu(C₁₄H₁₈NO₂)₂], the Cu^II ion, lying on an inversion centre, is four-coordinated by two imine N and two phenolate O atoms from two Schiff base ligands, forming a slightly distorted square-planar geometry.

Bis{2-meth-oxy-6-[(3-methoxy-prop-yl)imino-meth-yl]phenolato-κN,O}copper(II)

The title complex, [Cu(C(12)H(16)NO(3))(2)], adopts a distorted square-planar coordination geometry with the Cu(II) ion situated on a crystallographic inversion center. The two Schiff base ligands are coordinated in a trans fashion. In the crystal structure, non-classical inter-molecular C-H⋯O hydrogen bonds involving the ether O atoms link the Schiff base mol-ecules into a two-dimensional network parallel to (101).

Tris[4-(2-pyridylmethyl-eneamino)phenol]iron(II) bis-(perchlorate)

In the title compound, [Fe(C(12)H(10)N(2)O)(3)](ClO(4))(2), the metal center is coordinated by six N atoms from the three bidentate chelating ligands in a distorted octa-hedral coordination geometry, with overall formation of the meridional (OC-6-21) isomer. Inter-molecular O-H⋯O hydrogen bonds between the hydroxyl groups of the cation and the counter-anions form an infinite one-dimensional chain in the c-axis direction.