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

Reaction of Zn(NO3)2·6H2O 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]·H2O (1) (PABA = p-aminobenzoic acid). Single-crystal X-ray diffraction reveals that 1 crystallizes in the orthorhombic system, space group P212121, 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⋯O, O–H⋯O hydrogen bonding and π–π 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.

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