Gökhan Kaştaş

Probing the compound (E)-5-(diethylamino)-2-[(4-methylphenylimino)methyl]phenol mainly from the point of tautomerism in solvent media and the solid state by experimental and computational methods

In this study, the molecular structure and spectroscopic properties of (E)-5-(diethylamino)-2-[(4-methylphenylimino)methyl]phenol were characterized experimentally by X-ray diffraction, FT-IR and UV-vis spectroscopic techniques and computationally by DFT method. It is concluded on the basis of X-ray diffraction and FT-IR analyses that the title compound exists in enol form in the solid state. UV-vis spectra of the title compound were recorded in different organic solvents to investigate the dependence of tautomerism on solvent types. The tautomerism-solvent relation was also studied by computational methods to have more insight on structural properties. The geometry optimization of the title compound in gas phase was performed by using DFT (B3LYP) method with 6-311G(d,p) basis set. The geometry optimizations in solvent media were carried out at the same theory level by the polarizable continuum model (PCM). In the calculation of excitation energies, TD-DFT calculations were carried out in both gas and solution phases. The computational investigation of non-linear optical properties indicates that the title compound has a good second order nonlinear optical property. The thermodynamic properties were obtained in the range of 100-500 K.

Synthesis, IR spectrum, thermal behaviour and crystal structure of a novel one-dimensional cyano-bridged zinc(II)/nickel(II) complex

Abstract The cyano-bridged heteronuclear coordination polymer of zinc(II)/nickel(II) has been prepared by N-(2-hydroxyethyl)-ethylendiamine (hydet-en), alternatively named 2-(2-aminoethylamino)-ethanol and characterised by IR and thermal analysis. In the bimetallic complex, the decomposition of hydet-en ligands is seen to be endothermic whereas that of the cyano ligands is found to be exothermic. The crystal structure of the complex has been determined by single-crystal X-ray diffraction. The crystal structure of the zinc(II)-nickel(II) complex consists of a one-dimensional polymeric chain –Zn(hydet-en)2–NC–Ni(CN)2–CN–Zn(hydet-en)2– in which the zinc(II) and nickel(II) atoms are linked to each other by the cyano groups. The shift and splitting of the cyano stretching vibration is also evidence for the formation of cyano bridges. The nickel atom has a square-planar arrangement with four cyanide-carbon atoms where two cyano groups are in terminal position and two further ones in a bridging position. The Zinc atom has a distorted octahedral arrangement with two cyano and two hydet-en ligands. Both cyano and hydet-en ligands act as N-donor ligands and ethanol groups of the hydet-en ligand are not involved in the coordination. The NH, NH2 and OH groups of the hydet-en ligand are involved in intra- or intermolecular hydrogen bonding.

Existence of a resonance hybrid structure as a result of proton tautomerism in (±)-(E)-4-Bromo-2-[(2,3-dihydroxypropylimino) methyl]phenol racemate

o-Hydroxy Schiff bases have two tautomers known as phenol-imine and keto-amine forms. In the present work, the tautomerism in (E)-4-Bromo-2-[(2,3-dihydroxypropylimino)methyl]phenol compound has been investigated by experimental (XRD, FT-IR and UV-vis) and computational (DFT and TD-DFT) methods. The X-ray diffraction (XRD) study reveals that the title compound favors a resonance hybrid structure of phenol-imine and keto-amine forms in the solid state rather than having these forms separately or jointly. Experimental UV-vis study of proton transfer process in solvent media (Benzene, DMSO and EtOH) shows the preference of phenol-imine form in benzene while both phenol-imine and keto-amine characteristics are present in EtOH and DMSO.

Single stranded helical chains of C-H⋯π interactions further connected by halogen-halogen interactions of type I to construct supramolecular structure of (E)-5-(diethylamino)-2-[(4-iodophenylimino)methyl]phenol compound.

In this study, (E)-5-(diethylamino)-2-[(4-iodophenylimino)methyl]phenol compound was investigated from the point of stacking interactions assembling the supramolecular network, conformational isomerism and tautomerism. For this purpose, X-ray diffraction, FT-IR and UV/Vis spectroscopic techniques were used, giving the following structural and spectroscopic properties of the compound: The title compound has two conformers (anti and eclipsed) in the crystal structure resulting from rotation about C-N single bond of ethyl group. Both conformers prefer enol form in the solid state, adopting E configuration about the CN double bond. The supramolecular architecture of the compound is constructed by two non-covalent interactions as C-H⋯π and halogen-halogen interactions. The repetition of C-H⋯π interactions is resulted in a single-stranded helical structure. The helical structures are further connected by C-I⋯I-C interactions of Type I to construct the two dimensional supramolecular network defined as (6,3)-net in Wells nomenclature. The title compound adopts both enol and keto forms in EtOH (a polar and protic solvent) while enol form is preferred in the solid state.

EPR and optical-absorption studies of Cu2+-doped Zn(NH2(CH2)3NHOH)2Ni(CN)4 single crystals

Electron paramagnetic resonance of Cu2+-doped catena-trans-bis(N-(2-hydroxyethyl)-ethylenediamine) zinc(II)-tetra-μ-cyanonicelate(II) [Zn(NH2(CH2)3NHOH)2Ni(CN)4] single crystals and powder are examined at room temperature. The spectra show the substitution of the Zn2+ ion with the Cu2+ ion. The crystal field around the Cu2+ ion is nearly axial. There is a single paramagnetic site withgxx=2.073,gyy=2.060,gzz=2.248,Axx=40.5 G,Ayy=50.8 G,Azz=172.0 G. The ground-state wave function is an admixture of dx2−y2 and dz2 states. The optical-absorption studies show two bands at 320 nm (31250 cm−1) and 614 nm (16286 cm−1) which confirm the axial symmetry. The crystal field parameters and the wave function are determined.

Survey of conformational isomerism in (E)-2-[(4-bromophenylimino)methyl]-5-(diethylamino)phenol compound from structural and thermochemical points of view

In this study, (E)-2-[(4-bromophenylimino)methyl]-5-(diethylamino)phenol compound was investigated by mainly focusing on conformational isomerism. For this purpose, molecular structure and spectroscopic properties of the compound were experimentally characterized by X-ray diffraction, FT-IR and UV-Vis spectroscopic techniques, and computationally by DFT method. The X-ray diffraction analysis of the compound shows the formation of two conformers (anti and eclipsed) related to the ethyl groups of the compound. The two conformers are connected to each other by non-covalent C-H⋯Br and C-H⋯π interactions. The combination of these interactions is resulted in fused R(2)(2)(10) and R(2)(4)(20) synthons which are responsible for the tape structure of crystal packing arrangement. The X-ray diffraction and FT-IR analyses also reveal the existence of enol form in the solid state. From thermochemical point of view, the computational investigation of isomerism includes three studies: the calculation of (a) the rate constants for transmission from anti or eclipsed conformations to transition state by using Eyring equation, (b) the activation energy needed for isomerism by using Arrhenius equation, (c) the equilibrium constant from anti conformer to eclipsed conformer by using the equation including the change in Gibbs free energy. The dependence of tautomerism on solvent types was studied on the basis of UV-Vis spectra recorded in different organic solvents. The results showed that the compound exists in enol form in all solvents except ethyl alcohol.

cis-Bis(butyl-amine-κN)bis-[sulfa-diazine(1-)-κN,N']copper(II) penta-hydrate.

In the title compound {systematic name: cis-bis[4-amino-N-(pyrimidin-2-yl)benzenesulfonamidato-κ2 N,N′]bis(butylamine-κN)copper(II) pentahydrate}, [Cu(C10H9N4O2S)2(C4H11N)2]·5H2O or [Cu(sdz)2(ba)2]·5H2O [ba is butylamine and sdz = sulfadiazine(1−)], the copper(II) cation is six-coordinated by four N atoms of two sulfadiazine ligands and two N atoms of butylamine ligands. The copper(II) ion and one of the water molecules lie on twofold rotation axes. One of the butyl groups is disordered over two sites, with occupancies of 0.395 (8) and 0.605 (8). The geometry around the S atom is distorted tetrahedral. The crystal structure involves intermolecular N—H⋯N and N—H⋯O hydrogen bonds. N—H⋯N hydrogen bonds between sdz ligands lead to a sheet structure parallel to the ab plane.

Analysis of tautomeric equilibrium in (E)-4,6-dibromo-2-[(4-fluorophenylimino)methyl]-3-methoxyphenol compound.

In this study, the tautomeric equilibrium between the phenol-imine and keto-amine structural forms of (E)-4,6-dibromo-2-[(4-fluorophenylimino)methyl]-3-methoxyphenol compound has been investigated with experimental (XRD, UV-vis and NMR) and theoretical (DFT and TD-DFT) methods. The results clearly show that structural preference of the compound is definitely depended on its state. Namely, the compound exists in phenol-imine form in the solid state while one or both of these forms can be seen in solvent media. For example, the compound prefers phenol-imine form in benzene while both forms exist in EtOH and DMSO solvents. Coexistence of two forms has been quantified with NMR studies, giving a ratio of 11:9 for phenol and keto structures of the compound in acetone-d6 solvent.

Bis(propane-1,3-diamine)­disaccharinatonickel(II)

In the title complex, [Ni(C7H4NO3S)2(C3H10N2)2] or [Ni(sac)2(pen)2] (sac = saccharinate or 1,1,3-trioxo-2,3-dihydro-1λ6,2-benzothiazol-2-ide and pen = propane-1,3-diamine), the NiII ion sits on an inversion center, being coordinated by two N atoms of the sac ligands, which occupy trans positions, and four N atoms of the bidentate pen ligands to define a distorted octahedral geometry. The pen ligands chelate the metal ion, forming a six-membered ring which adopts a half-chair conformation, while the sac ligands adopt the most common coordination mode. The crystal packing is stabilized by N—H⋯O hydrogen bonds, which form a one-dimensional network along [010]. It is also supported by an N—H⋯S hydrogen bond between the amine group of the pen ligand and the sulfonyl group of the sac ligand.

Supramolecular structure constructed by coordination dimer of pyromellitate ligand

The mixed-ligand coordination dimer [Mn 2 (H 2 O) 2 (Hpm) 2 (ina) 2 ].H 2 O (Hpm=trianion of pyromellitic acid, ina=isonicotinamide) was investigated predominantly with regard to supramolecular architecture in the crystal packing. The structural properties of the complex were characterized by X-ray diffraction (XRD) technique and Fourier transform infrared (FTIR) spectroscopy. The [Hpm]3anion bridges Mn(II) ions with a tridentate coordination mode through its carboxylate groups in cis positions. In the formation of the 1D chain structure in the complex, the amide group of the ina ligand and the aqua ligand are involved in DD:AA type H-bonding with the COOgroup of [Hpm] 3. The FT-IR investigation of the complex was performed within the mid-IR region, mainly focusing on the characteristic vibrations of pyromellitic acid and isonicotinamide moieties by considering their free states and ligand behaviour in the case of complex formation.