Two Porous Zinc Coordination Polymers with (10,3) Topological Features Based on a N-Centered Tripodal Ligand and the Conversion of a (10,3)-d Subnet to a (10,3)-a Subnet

Two porous (3,4)-connected zinc coordination polymers, {[Zn(TIPA)(mal)_1/2](NO₃)·3H₂O}_n (1) and {[Zn(TIPA)(glu)_1/2](NO₃)·H₂O}_n (2) (mal = malonic acid, glu = glutaric acid, TIPA = tris(4-(1H-imidazol-1-yl)phenyl)amine) have been hydrothermally synthesized and characterized. Complex 1 crystallizes in the orthorhombic space group Pnna (No. 52) containing an unusual 3D subnet with (10,3)-d topology and left- and right-handed helical channels. Complex 2 crystallizes in the orthorhombic chiral space group P222₁ (No. 17) containing an unusual 3D chiral subnet with (10,3)-a topology and 4-fold right-handed helical channels. The conversion of achiral complex 1 with a (10,3)-d (utp) achiral subnet to chiral complex 2 with a (10,3)-a (srs) chiral subnet has been successfully induced by increasing the length of ditopic aliphatic dicarboxylic acid. Second harmonic generation (SHG) measurement was performed on complex 2 revealing that 2 has a strong SHG response, and the SHG efficiency is approximately 0.8 times that of urea (ca. 8 times that of KDP). In addition, photoluminescence and thermogravimetric analysis were also performed on 1 and 2.