Syntheses, Structures, and Properties of a Series of Polyazaheteroaromatic Core-Based Zn(II) Coordination Polymers Together with Carboxylate Auxiliary Ligands

Six Zn(II) coordination polymers, [Zn(H 2 L)(Hipa-CH 3 ) 2 ]·2H 2 O ( 1 ), [Zn 2 (HL) 2 (ipa-CH 3 )] ( 2 ), [Zn 2 (HL) 2 (ipa-NO 2 )]·2H 2 O ( 3 ), [Zn 2 (HL) 2 (ipa-NO 2 )] ( 4 ), [Zn 2 (HL)(BTCA)(H 2 O)]·H 2 O ( 5 ), and [Zn 3 (HL) 3 (BTCA)] ( 6 ), were synthesized by reactions of Zn(II) salts with rigid ligand 1-(1 H -imidazol-4-yl)-4-(4 H -tetrazol-5-yl)benzene (H 2 L) and different carboxylic acids, 5-methyl-isophthalic acid (H 2 ipa-CH 3 ), 5-nitro-isophthalic acid (H 2 ipa-NO 2 ), and 1,2,4-benzenetricarboxylic acid (H 3 BTCA). Complexes 1 and 2 were formed under different pH values, and 1 is a one-dimensional (1D) chain extended by hydrogen bonds and π–π stacking interactions to form a three-dimensional (3D) supramolecular polymer, while 2 exhibits a uninodal 6-connected 3D architecture with (4 12 ·6 3 )- pcu topology based on the binuclear Zn(II) secondary building units (SBUs). Polymers 3 and 4 present a pair of pseudopolymorphs with layered-pillared framework. Polymer 3 possesses Zn 2 (HL – ) 2 2+ sheets pillared by the ipa-NO 2 2– ligand to form a 3D net, while 4 builds on the [Zn 2 (HL)(ipa-NO 2 )] + layer pillared by HL – ligand. Complex 5 is a (3,8)-connected tfz-d 3D net with point (Schläfli) symbol (4 3 ) 2 (4 6 ·6 18 ·8 4 ) based on the tetranuclear [Zn 4 (COO) 4 ] SBUs, while the BTCA 3– ligands act as three-connector pillars to link adjacent [Zn 3 (HL – ) 3 ] 3– layers into a 3D net for 6 . Complexes 1 – 6 exhibit intense light blue emission in the solid state at room temperature, and activated sample 6 shows highly selective CO 2 uptake over N 2 and H 2 .