Syntheses, structure and properties of Alkaline-earth metal salts of 4-Nitrophenylacetic acid

Abstract

The synthesis, crystal structure, spectral characteristics and thermal properties of alkaline-earth metal salts of 4-nitrophenylacetic acid (4-npaH) namely, [Mg(H 2 O) 6 ](4-npa) 2 •4H 2 O (4-npa = 4-nitrophenylacetate) (1), [Ca(H 2 O) 2 (4-npa) 2 ] (2) and [Sr(H 2 O) 3 (4-npa) 2 ]•4.5H 2 O(3) are reported. In 1, the 4-npa ion functions as a charge balancing counter anion for the octahedral [Mg(H 2 O) 6 ] 2+ unit with the Mg(II) ion situated on a centre of inversion. The two unique lattice water molecules link the [Mg(H 2 O) 6 ] 2+ cations and 4-npa anions with the aid of O-H• • • O interactions. Compounds 2 and 3 are one-dimensional (1-D) coordination polymers containing an eight coordinated Ca(II) situated in a general position and a nine coordinated Sr(II) located on a twofold axis. The μ 2-bridging tridentate binding modes of the crystallographically independent 4-npa ligands in 2 and the unique 4-npa ligand in 3 link the bivalent metal ions into an infinite chain with alternating Ca• • • Ca separations of 3.989 and 4.009 Å, respectively, and a single Sr• • • Sr separation of 4.194 Å in the 1-D chain.