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Derivatives of quinolinium iodide have been found to exhibit second-order nonlinear optical (NLO) response in their crystalline form. The quaternary amine functionality is introduced as an electron-withdrawing group in NLO-active chromophores. While their electron-accepting capabilities are somewhat weaker than those of the nitro group, these organic salts show a much more favorable transparency−nonlinearity tradeoff for blue second harmonic generation (SHG) NLO applications. Here we present crystal growth and characterization via X-ray diffraction (XRD), NMR, FTIR, and optical spectroscopy measurements. Experimental linear optical features are fully consistent with INDO/SCI−SOS theoretical calculations. These latter provide a rationale for the NLO response of these materials. Calculations predict a sizable molecular nonlinearity, which parallels the wavelength of the lowest charge-transfer transition. In addition, a direct correlation between SHG powder response to the β crystallographic angle is observed.

Copolymers containing second-order nonlinear optical (NLO) active transition metal complexes into the main chain were synthesized and characterized by matrix-assisted laser desorption ionization−time of flight mass spectrometry (MALDI−TOF MS), TG, and DSC analyses for the first time. The Cu(II) complex Ia of the N,N‘-bis(2,4-dihydroxybenzylidene)-1,2-phenylenediamine ligand was synthesized and used as the NLO unit. The polycondensation between the copper(II) complex Ia (NLO unit) and butanediol bischloroformate was performed to obtain the exactly alternating copolycarbonate II. Two copolyethers, III and IV, containing different amounts of NLO units in the main chain (10% and 47%, respectively), were obtained by reaction of dibromomethane and suitable mixtures of the Cu(II) diimine complex Ia and bisphenol A in different molar ratios. The resulting copolymers II−IV were characterized by MALDI−TOF MS. The structure of low molecular weight oligomers contained in each polymeric sample inferred by MALDI spectra was found diagnostic of their composition and microstructure. Copolymers II−IV exhibit very good thermal stability and are promising candidates for second-order NLO materials.

The ground state configuration and the electronic structure of the title compound have been investigated by relativistic effective core potential configuration interaction ab initio calculations and He I/He II UV photoelectron spectroscopy. It has been found that the ⁴A‘‘ [(a‘)¹ (a‘‘)¹ (a‘)¹] state, associated with the 5f³ uranium configuration, represents the molecular ground state and is close in energy to the higher-lying ⁴A‘‘ (5f² 6d¹) state. The comparison of the present photoelectron data and theoretical results with those reported for analogous lanthanide complexes indicates close similarities in metal−ligand bonding between the 4f and 5f M(III) organometallics. The relative stability of the 5f³ versus 5f² 6d¹ uranium ion configuration correlates with the inherent chemical stability of U(III) organometallics, compared to that of the Th(III) (6d¹) analogues. The easier M(IV) → M(III) reduction for U(IV) relative to Th(IV), the numerous examples of reductive elimination processes in U(IV) organometallic chemistry, and the greater Th−R versus U−R experimental homolytic bond disruption energies in cyclopentadienylactinide(IV) alkyls can all be rationalized in terms of the differing electronic stabilities of the U(III) and Th(III) ground states.

A new Schiff-base ligand based on the condensation of diaminomaleonitrile and 4-(diethylamino)salicylaldehyde is reported with its copper, nickel, and zinc complexes. Their second-order nonlinear optical properties are investigated by electric field induced second harmonic (EFISH) and ZINDO quantum-chemical calculations to probe the role of the metal center in the nonlinearity. All the complexes exhibit a second-order nonlinear response that is larger than that of the ligand with an hyperpolarizability (β) value of 400 (±100) 10^-30 cm⁵ esu^-1 for the zinc derivative at 1.34 μm. Theoretical calculations indicate that the two-level model is inadequate to describe the nonlinearity in such systems.

The first ab initio study of bonding and bonding energetics in zerovalent rare earth bis(arene) sandwich complexes is presented. The d³ ground state and d²s¹ first excited state [(e2g)³ and (e2g)²(a1g¹) configurations, respectively] electronic structures and geometries of the M(η⁶-C6H6)2 complexes, where M = Y and Gd, have been investigated by using relativistic effective core potentials with MP2, MP4, and coupled-cluster ab initio wave functions. The two electronic states lie close in energy but exhibit significant differences in bonding interactions and geometries. The greater stabilities found in the ground states of both complexes are associated with greater metal → ligand back-bonding interactions and, hence, shorter M−C bond lengths. Computed ground state electronic configurations agree well with experimental EPR and magnetic susceptibility data, while metrical parameters are in very good agreement with diffraction data. The metal−arene interactions, both ligand-to-metal donation and metal-to-ligand back-donation, are similar in both complexes. The role of electron correlation appears crucial to correctly predicting the metal−arene dissociation energies. The Hartree−Fock energy is actually repulsive compared to that of the ground state fragments, while the inclusion of correlation effects through perturbative and coupled-cluster procedures predicts bound molecules, even though the binding energies remain underestimated.