Synthesis and structural characterization of a barium coordination polymer based on a μ₂-monoatomic bridging 4-nitrobenzoate

Abstract

The synthesis, spectral characterization, crystal structure and properties of [Ba(H₂O)₂(NMF)₂(4-nba)₂], 1 (NMF = N-methylformamide; 4-nba = 4-nitrobenzoate), are reported. ¹H and ¹³C NMR spectral data reveal the presence of NMF in 1. A strong band at 1660 cm⁻¹ in the infrared spectrum indicates the binding of amide oxygen to Ba(II) which is confirmed by the single crystal structure. The unique Ba(II) in 1 situated on a mirror plane exhibits nine coordination and is bonded to two symmetry related monodentate terminal NMF ligands via the amide oxygen, and a terminal aqua ligand. The μ₂-monoatomic bridging binding mode of each of a crystallographically independent 4-nba ligand and a unique water ligand link the Ba(II) cations into an infinite chain extending along a, leading to the formation of a 1D coordination polymer with Ba···Ba separations of 4.2522(3) Å. In the chain, the {BaO₉} polyhedra are linked in a face sharing fashion. Thermal decomposition of 1 results in the formation of BaCO₃ residue. A comparative study of the structural chemistry of several barium coordination polymers is described.

Graphical Abstract

Keywords:

• Barium
• N-methylformamide
• 4-nitrobenzoate
• μ₂-monoatomic bridging
• coordination polymer

Acknowledgments

The authors thank the Sophisticated Analytical Instrument Facility (SAIF), Indian Institute of Technology (IIT) Madras for single crystal X-ray analysis of 1 reported in this paper. The authors thank one of the reviewers for useful suggestions.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

BRS thanks the University Grants Commission (UGC), New Delhi for financial support to the School of Chemical Sciences (formerly Department of Chemistry), at the level of DSA-I under the Special Assistance Program (SAP) vide letter F.No. 540/14/DSA-I/2015/(SAP-I). PHB is a recipient of the BSR Fellowship (Supernumerary fellowship for “Single Girl Child”) by UGC, New Delhi vide letter F.No.25-1/2014-15(BSR)/7-69/2007(BSR).