Iftikhar Hussain Bukhari

Prediction of robustly large molecular second-order nonlinear optical properties of terpyridine-substituted hexamolybdates: structural modelling towards a rational entry to NLO materials.

We have explored an innovative, versatile, and novel molecular hybrid containing polyoxometalate (POM) cluster linked with terpyridine ligand via pi-bridged donor-acceptor (D-A) configuration. The dipole polarizabilities, density of states, and second-order nonlinear optical (NLO) properties of terpyridine-substituted hexamolybdates have been investigated by using time-dependent density functional response theory (TDDFT). This class of organic-inorganic hybrid compounds possesses a robustly large molecular second-order NLO response, especially [Mo(6)O(18)(N(4)C(25)H(16)I(2))](2-) (system 5) and [Mo(6)O(17)(N(4)C(25)H(16)(CN)(2))(N(4)C(25)H(16)(CN)(2))](2-) (system 10) with the static second-order polarizability (beta(vec)) computed to be 1209.25x10(-30)esu and 1622.67x10(-30)esu respectively. Thus, these systems have the possibility to be excellent second-order nonlinear optical materials. Analysis of the major contributions to the beta(vec) value suggests that the charge transfer (CT) from POM-cluster to terpyridine ligand (D-A) along the z-axis plays the key role in the NLO response, POM-cluster (hexamolybdates) acts as a donor (D) whereas terpyridine ligand acts as an acceptor (A) in all the studied systems. The computed beta(vec) values increase by the incorporation of electron acceptors (halogen=F, Cl, Br and I) at the terminus of terpyridine ligand. Furthermore, substitution of trifluoromethoxy (-OCF(3)), trifluoromethyl (-CF(3)), and cyanide (-CN) at the end of terpyridine ligand respectively enhances the optical nonlinearity. Orbital analysis shows that the degree of CT between POM and terpyridine segment was increased in 2D and organometallic/POM hybrid systems. The present investigation provides important and thought provoking insight into the robustly large NLO properties of terpyridine-substituted hexamolybdates.

2-(2-Oxo-2-phenyl­ethyl)-1,2-benziso­thia­zol-3(2H)-one 1,1-dioxide

In the title compound, C15H11NO4S, the benzothiazole unit is essentially planar [maximum deviation = 0.0644 (14) Å for the N atom] and forms a dihedral angle 54.43 (6)° with the phenyl ring. In the crystal structure, weak bifurcated C—H⋯O hydrogen bonds involving the carbonyl O atoms as acceptors result in R 2 2(7) ring motifs.

2-[2-(3-Chloro-phen-yl)-2-oxoeth-yl]-1,2-benzisothia-zol-3(2H)-one 1,1-dioxide.

In the title compound, C15H10ClNO4S, the benzothiazole ring system is essentially planar [maximum deviation = 0.0382 (13) Å for the N atom] and forms a dihedral angle of 74.43 (6)° with the chloro-substituted benzene ring. In the crystal structure, weak intermolecular C—H⋯O hydrogen bonds form R 2 2(10) and R 2 2(16) ring motifs

3,4-Dimethyl-2-(2-oxo-2-phenyl-eth-yl)-2H,4H-pyrazolo-[4,3-c][1,2]benzothia-zine-5,5-dione.

In the title molecule, C19H17N3O3S, the heterocyclic thiazine ring adopts a half-chair conformation with the S and N atoms displaced by 0.530 (5) and 0.229 (6) Å, respectively, on opposite sides of the mean plane formed by the remaining ring atoms. The ethanone group lies at an angle of 3.8 (3)° with respect to the benzene ring, which lies almost perendicular to the pyrazole ring, with a dihedral between the two planes of 89.22 (11)°. Weak intermolecular C—H⋯O hydrogen-bonding interactions are present.