Structural diversity in a copper(II)/isophthalato/9-methyladenine system. from one- to three-dimensional metal-biomolecule frameworks

摘要

The synthesis, X-ray single crystal structure analyses, and physicochemical characterization of copper(II)-isophthalato coordination polymers containing the 9-methyladenine nucleobase {[Cu(μ-iso)(9Meade)(H_2O) _2]}_n (1), {[Cu(μ-iso)(μ-9Meade)]}_n (2), {[Cu_2(μ_4-iso)_2(9Meade)_2] ·2H_2iso}_n (3), {[Cu_2(μ_3- iso)_2(μ-9Meade)(H_2O)]·H_2O} n (4), and {[Cu_2(μ_3-iso)_2(μ- 9Meade)(H_2O)_2]·1.5H_2O}_n (5) (where iso = isophthalato and 9Meade = 9-methyladenine) are reported. Compound 1 contains neutral chains in which the isophthalato dianion acts as a bridging ligand, while the methylated nucleobase behaves as N7-coordinated terminal ligand. Compound 2 exhibits a two-dimensional network in which the aromatic dicarboxylate ligand and the nucleobase act as bidentate bridging ligands. Compound 3 is based on dimeric paddle-wheel shaped entities in which the copper(II) atoms are bridged by means of four isophthalato ligands to give a NO_4 chromophore with the N7 nitrogen atom of the 9-methyladenine filling the axial position. The linkage of the dimeric entities through the second carboxylate group of the dianions leads to covalent layers that are further connected to give a supramolecular three-dimensional pillared structure by means of hydrogen bonding and π-π interactions involving noncoordinated isophthalic acid molecules. Compounds 4 and 5 contain paddle-wheel [Cu _2(μ-iso)_4(9Meade)_2] entities and [Cu(H _2O)] or [Cu(H_2O)_2] units connected by means of the isophthalate and 9-methyladenine bidentate bridging ligands.