A second-order nonlinear optical material prepared through in situ hydrothermal ligand synthesis

The in situ hydrothermal reactions of ZnCl2 With benzonitrile, 2-amino-5-cyanopyridine, and trans-2,3-dihydro-2(4"-cyanophenyl)-benzo[e]indole in the presence of NaN3 and water afford two 3D-diamond-like networks, (CN4-C6H5)(2)Zn (1) and (NH2-C5H3N-CN4)(2)Zn (2), and one 2D square grid network, [(CN4-C6H4-C12H7N-C5H4N)(2)Zn]center dot 1.5H2O (3), in which these ligands gradually involve a noncenter-A-D (acceptor-donor) system, a one-centerA-D system, and a two-center-A-D system, respectively. All three compounds crystallize in noncentrosymmetric space groups (l (4) over bar 2d for 1 and 2 and Fdd2 for 3) and display strong second harmonic generation (SHG) responses. Among the three new complexes, 3 shows the largest SHG effect, which is about 50 and 500 times that of urea and KDP (KH2PO4), respectively. The two-center-A-D system (multicenter push-pull electronic effect) in 3 may be responsible for it having the largest SHG effect. Interestingly, the three compounds exhibit strong fluorescent emissions at different wavelengths, 1 and 2 with blue fluorescent emissions at 390 and 415 nm and 3 with yellow-green fluorescent emissions at 495 and 532 nm.