title: Prediction of robustly large molecular second-order nonlinear optical properties of terpyridine-substituted hexamolybdates: structural modelling towards a rational entry to NLO materials.
abstract: 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.
authors.affiliation: Key Laboratory of Polyoxometalate Science of Ministry of Education, Faculty of Chemistry, Northeast Normal University, Institute of Functional Material Chemistry, Changchun 130024, Jilin, PR China. dr_janjua2010@yahoo.com
authors.forename: Muhammad Ramzan Saeed Ashraf
authors.initials: MR
authors.lastname: Janjua
authors.forename: Wei
authors.initials: W
authors.lastname: Guan
authors.forename: Likai
authors.initials: L
authors.lastname: Yan
authors.forename: Zhong-Min
authors.initials: ZM
authors.lastname: Su
authors.forename: Muhammad
authors.initials: M
authors.lastname: Ali
authors.forename: Iftikhar Hussain
authors.initials: IH
authors.lastname: Bukhari
mesh_terms: D003198:Computer Simulation; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D008982:Molybdenum / Q000737:chemistry*; D055095:Optics and Photonics / Q000295:instrumentation* / Q000379:methods; D011725:Pyridines / Q000737:chemistry*; D013329:Structure-Activity Relationship
chemical_list: D008024:Ligands; D011725:Pyridines; C044659:molybdate; D008982:Molybdenum