Isoreticular Chemistry and Applications of Supramolecularly Assembled Copper-Adenine Porous Materials

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.

Drug-delivery and biological activity in colorectal cancer of a supramolecular porous material assembled from heptameric chromium-copper-adenine entities

The therapeutic application of drugs often faces challenges due to non-specific distribution, inadequate dosification and degradation, which limits their efficacy. Two primary strategies are employed to overcome these issues: the use of derivatives of the active substances and incorporation of those into porous materials. The latter, involving materials such as zeolites, metal-organic frameworks (MOFs), and hydrogels, has shown promising results in protecting the active ingredients from degradation and enabling a controlled release. This study focuses on supramolecular metal-organic frameworks (SMOFs), which leverage supramolecular interactions for enhanced pore size control. [Cu6Cr(μ-adeninato-κN3:κN9)6(μ3-OH)6(μ-OH2)6](SO4)1.5·nH2O (Cu6Cr) was chosen for its flexible porous structure, water-stability, and paramagnetic properties. Magnetic sustentation studies showed that this compound was able to capture several drug molecules: 5-fluorouracil (5-FU), 5-aminosalicylic acid (5-ASA), 4-aminosalicylic acid (4-ASA) and theophylline (THEO). Their release follows a pseudo-first-order kinetics with desorption half-lives ranging from 2.2 to 4.7 hours. In this sense, a novel approach is proposed using bulkier raffinose and cholesterol as pore-blocking molecules. Cholesterol exhibited the best performance as a blocking molecule increasing the desorption half-life up to 8.2 hours. Cytotoxicity and RNA-seq transcriptomic assays carried out on human colorectal cancer cell cultures showed, on one hand, that the Cu6Cr porous material exhibits a proliferative effect, probably coming from the over-expression of MIR1248 and SUMO2 genes, and on the other hand, that there is a delay in the emergence of the cytotoxicity of 5-FU as expected for a slower release.

Crystal Engineering and Self-Assembled Nanoring Formation with Purine-CdII /HgII Supramolecular Frameworks

We report three complexes of CdII and HgII with two purine rare tautomers, N9-(pyridin-2-ylmethyl)-N6 -methoxyadenine, L1 and N7-(pyridin-2-ylmethyl)-N6 -methoxyadenine, L2, highlighting diverse crystallographic signatures exhibited by them. Influence of substituents, binding sites, steric effects and metal salts on the different modes of binding enabled an insight into metal-nucleobase interactions. L1 interacted with two and three equivalents of Cd(NO3 )2 .4H2 O and HgCl2 , respectively, while L2 interacted with two equivalents of HgCl2 , altogether leading to three different complexes (1 [C48 H48 Cd6 N34 O50 ], 2 [C12 H12 Cl4 Hg2 N6 O] and 3 [C12 H12 Cl2 HgN6 O]) possessing varied dimensionality and stabilising interactions. The photoluminescent properties of these coordination frameworks have also been probed. Notably, nanoring-like structures were obtained, as a result of self-assembly of 3 when investigated by transmission electron microscopy, additionally supported by molecular dynamics simulations.