Synthesis, structure and spectroscopic properties of oxovanadium tris(3,5-dimethylpyrazolyl)borate aroylthiourea complexes

Aroylthiourea ligands, 1-aroyl-3-cyclohexyl-3-methylthiourea (HL1), 1-(2-chloroaroyl)-3-cyclohexyl-3-methylthiourea (HL2), 1-(3-chloroaroyl)-3-cyclohexyl-3-methylthiourea (HL3) and 1-(4-chloroaroyl)-3-cyclohexyl-3-methylthiourea (HL4) were synthesized through a condensation reaction of methylcyclohexylamine and aroylisothiocyanate with a general formula (X-Ph)(CO)NH(CS)N(C6H5)(CH3) where X = H, o-Cl, m-Cl and p-Cl, fully characterized by CHNS micro elemental analysis, infrared spectroscopy, UV-visible, nuclear magnetic resonance (1H, 13C) and X-ray crystallography. 1-(3-chloroaroyl)-3-cyclohexyl-3-methylthiourea (HL3) crystallized in the monoclinic system, a=14.504(3), b=4.9599(11), c=22.325(5) Å, β=98.461(7)°, Z= 4 and V=1588.5(6) Å with space group P21/c. The IR spectra of the ligands exhibits the characteristic v(CO) and v(N-H) at range 1701-1640 cm-1 and 3317-3144 cm-1, respectively. Whereas the 1H and 13C NMR spectra shows the resonances for N-H and -CO groups at range 8.3-8.5 and 160-163 ppm, respectively. A one-pot reaction involving the aroylthiourea ligand, oxovanadium(IV) ion and potassium hydrotris(3,5-dimethylpyrazolyl)borate (KTp*) complex gave the desired [oxovanadium(IV)(tris(pyrazolyl)borate)(aroylthiourea)] complexes namely Tp*VOL1, Tp*VOL2, Tp*VOL3 and Tp*VOL4 and all complexes were characterized accordingly. X-ray study showed that Tp*VOL1 adopted a monoclinic crystal, a=3.415(2), b=19.463(3), c=14.22(3) Å, β=107.411(4)°, Z= 4 and V=3542.7(11) Å with P21/c space group. The VO2+ center adopted a pseudo-octahedral geometry O2N3S, with the oxovanadium(IV) coordinated to the bidentate ligand (X-Ph)(CO)NH(CS)N(C6H5)(CH3) and tridentate Tp* ligands. The results showed that aroylthiourea ligands behave as bidentate chelate through O and S atom and the Tp* C3v symmetry adds stabilization to the VO2+ through its protective tripodal geometry

Experimental and DFT investigation on the influence of electron donour/acceptor on the hydrogen bonding interactions of 1-(1,3-Benzothiazol-2- y1)-3-(R-benzoylthiourea)

The presence of two different chromophores in benzothiazole molecule namely benzothiazole and aromatic rings lead to interesting chemical and biological properties that attract more researches on the compounds. Three new benzothiazolyl-benzoythiourea compounds namely 1-(1,3-benzothiazol-2-yl)-3-(benzoylthiourea) (BBT), 1-(1,3-benzothiazol-2-yl)-3-(4-chlorobenzoylthiourea) (BBT-4Cl) and 1-(1,3-benzothiazol-2-yl)-3-(4-methoxybenzoylthiourea) (BBT-4OCH3) with different electron withdrawing substituents (R) at the para positions on the benzene ring of benzoylthiourea ring have been synthesized from the reaction of R-benzoyl isothiocyanate (R= H, Cl, and OCH3) and 2-aminobenzothiazole. The compounds were characterized by spectroscopic techniques (infrared, 1H proton NMR and UV-Vis). The IR spectra showed the frequency signals of n (C=O), n (C=S), n (N-H) at 1664-1673, 1238-1249 and 3031-3055 cm-1, respectively. The 1H proton NMR spectra showed the presence of N-H amine and amide signals in the region of (12.14-12.35) and (14.17-14.43) ppm, respectively. The proton signals of the two benzothiazole and benzoylthiourea moieties appear at 7.08-8.16 ppm. A theoretical study based on Density Functional Theory (DFT) and Time-Dependent (TD) DFT was conducted to optimize the geometrical structure and investigate the electronic properties of title compounds. The highest occupied molecular orbital (HOMO) was found on the benzothiazole moiety; while, the lowest-unoccupied molecular orbital (LUMO) was located at the benzoylthiourea fragment. The DFT optimized structures possessed an intramolecular hydrogen bonding and the types of para substituents used influenced the properties of hydrogen bonding