A Unique Example of Structural Diversity Tuned by Apparently Innocent o-, m-, and p-Nitro Substituents of Benzoate in Their Complexes of Mn(II) with 4,4′-Bipyridine: 1D Ladder, 2D Sheet, and 3D Framework

Abstract

Four new Mn(II) coordination polymers [Mn(4,4′-bpy)(C6H5COO)2] n (1), [Mn(4,4′-bpy)(o-(NO2)C6H4COO)2] n (2), [Mn(4,4′-bpy)(m-(NO2)C6H4COO)2] n (3), and [Mn(4,4′-bpy)(p-(NO2)C6H4COO)2] n (4) (where 4,4′-bpy = 4,4′-bipyridine) have been synthesized by self-assembly of the primary ligands, benzoate and the o-, m-, and p-isomers of nitrobenzoates, respectively, together with 4,4′-bpy as the secondary spacer. All four complexes were characterized by elemental analyses, IR spectroscopy, single-crystal X-ray diffraction analyses, and variable-temperature magnetic measurements. The structural analyses reveal that complexes 1 and 3 are constructed by linear fused chains through double syn-syn (for 1) or syn-anti (for 3) carboxylate-bridged Mn(II), which are further linked to one another by trans coordinated 4,4′-bpy bridges, giving rise to a rectangular grid-like two-dimensional (2D) net. Complex 2 features one-dimensional (1D) molecular ladder formed by both syn-syn and syn-anti carboxylate-bridged dimeric Mn(II) units which are joined alternately by 4,4′-bpy. Complex 4 is formed by fused zigzag chains of double syn-syn carboxylate-bridged Mn(II) that are connected by cis oriented 4,4′-bpy to generate an unprecedented three-dimensional (3D) framework. The dimensionality of the complexes thus varies from 1D to 2D to 3D on changing the position of the nitro group from o- to m- to p- in the benzoate, showing explicitly the tuning ability of this apparently innocent substituent on the topology of the coordination polymer. Variable-temperature (1.8–300 K) magnetic susceptibility measurements showed the presence of antiferromagnetic coupling in all four complexes that have been fitted with an infinite classical-spin chain model derived by Fisher for 1, 3, and 4 (J = −0.779(2), −0.855(2), and −0.536(2) cm–1, respectively) and van Vleck equation for 2 (J = −0.354(2) cm–1).

Synthesis and Crystal Structure of a Mn(II) Metal-Organic Framework Based on a Polydentate Schiff Base Ligand

“…In summary, we have presented a 2D coordination polymer {[MnL 2 (NCS) 2 ]·(H 2 O) 4 } n (1) based on the Schiff base ligand bis(pyridin-3-ylmethylene)biphenyl-2,2 -dicarbohydrazide (L). The crystal and molecular structure of 1 has been determined on single crystals.…”

“…In particular, the incorporation of Mn(II) into metalorganic frameworks has received increasing attention in the fields of supramolecular chemistry and crystal engineering for the remarkable performances of the products in magnetical systems, catalysis and biochemistry [4,5]. Generally, the syntheses of MOFs are based on a self-assembly of organic ligands and metal ions or clusters, counterions, and solvent systems [6,7].…”

“…In addition, the linear triatomic pseudohalide SCN − is a frequently used anionic auxiliary ligand, which can coordinate through either the S or N atom to a metal center [23 -28]. In the present paper, through the assembly of the biphenyl-based Schiff base ligand L, the SCN − anion and the Mn(II) cation, a twodimensional MOF {[MnL 2 (NCS) 2 ]·(H 2 O) 4 } n (1) was synthesized and characterized especially by singlecrystal X-ray diffraction analysis.…”

Synthesis and characterization of four novel manganese(II) chains formed by 4,4′-azobis(pyridine) and benzoate or nitrobenzoates: Stabilization of unusual ladder structures

“…This low number contrasts with the more than two hundred examples found with 4,4 0 -bipyridine (4,4 0 -bpy) instead of 4,4 0 -azpy [47][48][49]. Given the interesting increase in the dimensionality (from a 1D ladder to a 2D sheet and a 3D network) that we have recently found in a group of carboxylate-bridged Mn(II) complexes with 4,4 0 -bpy [49], we have decided to explore the supramolecular structural changes induced by these four benzoate ligands when used with 4,4 0 -azpy instead of 4,4 0 -bpy. Thus here we report the synthesis, single crystal X-ray structures and magnetic properties of four new manganese(II) polymers based on the ligand 4,4 0 -azpy with benzoate and different benzoate derivatives: [Mn(4,4 0 -azpy)(C 6 H 5 COO) 2 ](4,4 0 -azpy) 0.5 (1), [Mn(4,4 0 -azpy)(p-(NO 2 )C 6 H 4-COO) 2 ] (2), [Mn(4,4 0 -azpy)(m-(NO 2 )C 6 H 4 COO) 2 ] (3) and [Mn(4,4 0 -azpy)(o-(NO 2 )C 6 H 4 COO) 2 (H 2 O) 2 ] (4).…”

“…However, this spacer has seldom been used to construct manganese(II)-based coordination polymers [38,39] and, in fact, a CCDC search (updated Feb. 2012) shows only nine Mn(II) complexes with the 4,4 0 -azpy ligand [36,39,[40][41][42][43][44][45][46] of which only one, recently reported, also contained a carboxylate ligand [46]. This low number contrasts with the more than two hundred examples found with 4,4 0 -bipyridine (4,4 0 -bpy) instead of 4,4 0 -azpy [47][48][49]. Given the interesting increase in the dimensionality (from a 1D ladder to a 2D sheet and a 3D network) that we have recently found in a group of carboxylate-bridged Mn(II) complexes with 4,4 0 -bpy [49], we have decided to explore the supramolecular structural changes induced by these four benzoate ligands when used with 4,4 0 -azpy instead of 4,4 0 -bpy.…”