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Published on: February 28, 2016
Coordination-Mode-Modulated Symmetry Breaking for Nonlinear Optical Crystals
Lan Wang1, Zhen Qin1, Shu-Fang Li1,2
1Key Laboratory of Functional Molecular Solids, Ministry of Education, College of Chemistry and Molecular Sciences, Anhui Normal University, Wuhu, Anhui241002, P. R. China.
Abstract:
Second-order nonlinear optical crystals are essential to photonics but face the challenge of combining large nonlinearity, high laser damage threshold, and suitable birefringence. We address this via a "multi-coordination-site-induced" strategy in metal complexes, employing d10 Cd2+ to induce second-order Jahn-Teller distortions alongside linear SCN- and planar π-conjugated ligands (pyrazole vs 1,2,4-triazolate). The centrosymmetric Cd(C3H4N2)2(SCN)2 (1) shows a wide bandgap (4.80 eV, Δn = 0.23), while the non-centrosymmetric Cd3(C2H2N3)4(SCN)2 (2) with distorted [CdN5S] octahedra achieves second-harmonic generation response [2.6 × KH2PO4], wide bandgap (4.60 eV), and moderate birefringence (0.18 at 546 nm), suitable for phase matching. Theoretical analysis attributes these properties to cooperative contributions of planar organic units and SCN- anions, confirming the effectiveness of this strategy.
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