Design, Structure And Properties Of Amino-acid-based Schiff Base Complexes And Metal-organic Frameworks

Extensive and continued interest exists in the design and construction of transition metal complexes with amino-acid-based Schiff bases, due to the wide range of potential applications in magnetism, nonlinear optics, luminescent probes and bioinorganic model compounds. Despite the wealth of studies in these systems, reports on the cobalt complexes of amino-acid based Schiff bases are far less in number. Meanwhile, it still remains a significant challenge for the assembly of higher dimensional (2D,3D) coordination polymers, possibly owing to the sparing solubility and unstability of the Schiff bases. On the other hand, considerable research has been devoted to the porous metal-organic frameworks (MOFs) for their fascinating topologies and promising applications as new materials. One of the efficient synthetic strategies for MOFs generation is the use of metal-carboxylate clusters known as the secondary building units (SBUs) that can be interconnected via various rigid organic linkers.The current studies on MOFs have indicated that SBUs can not only prevent the porous framework interpenetration and rigidify the framework, but also exhibit intriguing magnetic properties that can be imparted to the whole framework. In this paper, fifteen complexes with structural discrepancy have been achieved from normal crystal growth and hydro(solvo)thermal synthesis, and then characterized by single-crystal X-ray diffraction, IR, PXRD, TGA, optical spectra and magnetic measurement.1. Seven transition metal complexes have been synthesized successfully by the assembly of Co(â…¡)/Zn(â…¡) ions and two similar Schiff bases, N-(2-hydroxy-1-naphthylmethylidene)-DL-alanine(H2napala) and N-(2-hydroxy-1-naphthylmethylidene)-glycine(H2napgly). These complexes exhibit diversified structures from mononuclear unit to3-fold interpenetrated diamond framework. By the employment of the bridging co-ligands, Extended higher dimensional (2D,3D) networks were obtained under solvo(hydro)thermal conditions. The thermal stabilities, magnetic properties, Optical properties and specific DNA cleavage reactions of some compounds were studied.2. Heating the carboxylate ligands and transition metal ions gave rise to four new MOFs based on different SBUs. The results demonstrated that the same starting materials can resulting in completely different framework structures depending on the reaction conditions used. N2adsorption measurements were performed to estimate the porosity of activated samples, and magnetic studies of complex8indicate the dominant antiferromagnetic coupling between Co(â…¡) centers.3. Three3D interpenetrated diamond frameworks were constructed from isonicotinic acid and its derivatives,4-(isonicotinamido)benzoic acid. The interpenetration degrees of the same diomond nets are well controlled by employing the bridging pyridyl-based carboxylate ligands with different lengths. Moreover, a pcu type Mn(â…¡) polymer were obtained unexpectedly.