Synthesis, characterization and NLO properties of a new 3D coordination polymer assembled from p-aminobenzoic acid

Reaction of Zn(NO3)(2)center dot 6H(2)O with p-aminobenzoic acid in a 1:2 molar ratio under ethanol medium at room temperature affords a new three dimensional (3D) coordination polymer [Zn(PABA)(2)]center dot H2O (1) (PABA=p-aminobenzoic acid). Single-crystal X-ray diffraction reveals that 1 crystallizes in the orthorhombic system, space group P2(1)2(1)2(1), a=7.614(2), b=11.133(3), c=16.869(4). 1 adopts a 3D open framework with H2O molecules in the cavities. PABA, acting as bridging ligand as well as coordinating ligand, adopts a different coordination mode to bridge Zn atoms and form the 3D supramolecular structure which is further stabilized by N-H center dot center dot center dot O, O-H center dot center dot center dot O hydrogen bonding and pi-pi stacking interactions. Powder second-harmonic generation (SHG) efficiency measurement with Nd:YAG laser (1064 nm) radiation shows that the SHG efficiency of 1 is equivalent to KDP crystal. The present work also demonstrates that the framework of 1 is retained after removal of the guest H2O molecules, and the H2O molecules can be reintroduced into the framework, indicating that this complex may also be used to generate porous materials. (C) 2009 Elsevier Masson SAS. All rights reserved.