Stoichiometry-Regulated Synthesis of Three Adenine-Based Coordination Polymers for Catalytic Excellence through the Synergistic Amalgamation of Coordinative Unsaturation and Lewis Basic Sites.

Nucleobase adenine is a promising candidate for synthesizing fascinating coordination polymers (CPs) due to the presence of five potential metal-ion binding centers. In recent years, CPs have emerged as promising Lewis acid-base centers containing heterogeneous catalysts for a wide range of organic transformations. However, the crucial role of stoichiometric regulations of the starting materials and their consequential impact on catalytic performance are rarely studied. Herein, we have synthesized three adenine (Ad)-based cadmium CPs with 5-nitro isophthalic acid (H2NIPA) by a mixed linker approach by tuning the substrate's stoichiometric proportion. The single-crystal X-ray diffraction analysis of the synthesized CPs, SSICG-11, [Cd(Ad)(NIPA)(H2O)]·H2O; SSICG-12, [Cd(Ad)2(NIPA)(H2O)]; and SSICG-13, [Cd4(Ad)(NIPA)3]·H2O·DMF, reveals that these three compounds exhibit distinct asymmetric units, each reflecting varying precursor proportions. Due to their high chemical stability and the presence of both Lewis acidic-basic sites, SSICG-11-13 were employed as heterogeneous catalysts for Hantzsch and Strecker reactions. However, SSICG-12 is more efficient due to its capacity to form an open metal sites (OMSs) and the presence of a higher number of adenine moieties. Overall, this study demonstrated the stoichiometrically controlled synthesis of adenine-based CPs and dissected their efficiency as a heterogeneous catalyst by correlating their structures and compositions.