| Summary: | Salen-type metal complexes have been actively studied for their nonlinear optical (NLO) properties, and push-pull compounds with charge asymmetry generated by electron releasing and withdrawing groups have shown promising results. As a continuation of our research in this field and aiming at solid-state features, herein we report on the synthesis of mononuclear copper(II) derivatives bearing either tridentate N<sub>2</sub>O Schiff bases L<sup>(a−c)−</sup> and pyridine as the forth ancillary ligand, [Cu(L<sup>a−c</sup>)(py)](ClO<sub>4</sub>) (<b>1a</b>−<b>c</b>), or unsymmetrically-substituted push-pull tetradentate N<sub>2</sub>O<sub>2</sub> Schiff base ligands, [Cu(5-A-5′-D-saldpen/chxn)] (<b>2a</b>−<b>c</b>), both derived from 5-substituted salicylaldehydes (sal) and the diamines (1<i>R</i>,2<i>R</i>)-1,2-diphenylethanediamine (dpen) and (1<i>S</i>,2<i>S</i>)-1,2-diaminocyclohexane (chxn). All compounds were characterized through elemental analysis, infrared and UV/visible spectroscopies, and mass spectrometry in order to guarantee their purity and assess their charge transfer properties. The structures of <b>1a</b>−<b>c</b> were determined via single-crystal X-ray diffraction studies. The geometries of cations of <b>1a</b>−<b>c</b> and of molecules <b>2a</b>−<b>c</b> were optimized through DFT calculations. The solid-state NLO behavior was measured by the Kurtz−Perry powder technique @1.907 µm. All chiral derivatives possess non-zero quadratic electric susceptibility (<i>χ</i><sup>(2)</sup>) and an efficiency of about 0.15−0.45 times that of standard urea.
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