One-pot synthetic approach to isolate a single isomer of bis(diethylenetriamine)cobalt(III) cation in bulk using benzoates and the isomeric effects of the cation on ion association with anions |
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| Authors: | Ritu Bala Amrinder Kaur |
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| Affiliation: | 1. Department of Chemistry, UGC Centre for Advance Studies-I, Guru Nanak Dev University, Amritsar, Indiarituhatta@yahoo.com;3. Department of Chemistry, UGC Centre for Advance Studies-I, Guru Nanak Dev University, Amritsar, India |
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| Abstract: | Using a one-pot synthetic approach, a single isomer of bis(diethylenetriamine)cobalt(III) cation, [Co(dien)2]3+ is obtained in bulk from the isomeric mixture (s-fac : u-fac : mer is 7 : 28 : 65) using sodium salts of benzoates (BBz-bromobenzoate, DNBz-dinitrobenzoate, MBz-methylbenzoate) in aqueous medium. Herein, we report the syntheses and characterization of three complexes of composition mer-[Co(dien)2]Cl(p-BBz)2·H2O (1), s-fac-[Co(dien)2](o,p-DNBz)3·H2O (2) and mer-[Co(dien)2]Cl(p-MBz)2·4H2O (3) in the continuation of our earlier work, where benzoate (Bz), p-chlorobenzoate (CBz), p-nitrobenzoate (NBz) and p-aminobenzoate (ABz) were used. The isomeric identification of complex cation was initially made on the basis of spectroscopic characterization (UV–visible, IR and NMR). The binding properties of [Co(dien)2]3+ with benzoates (p-BBz, o,p-DNBz, p-MBz, Bz, CBz, NBz or ABz) have been studied using standard UV–visible spectroscopic titrations in aqueous medium and comparison indicate ion association constants of s-fac > mer. The single-crystal X-ray diffraction structure analysis of 3 reveals the presence of discrete ions ([Co(dien)2]3+, chloride, p-MBz) along with four lattice water molecules. The structure of 3, with formula [Co(dien)2](p-MBz)2Cl·4H2O, consists of alternating layers made of benzoate ions and layers made of [Co(dien)2]3+, chloride and water molecules. These layers result in the formation of their respective columns and intermolecular cohesion of p-MBz within the columns of [Co(dien)2]3+ is achieved via electrostatic and H-bonding interactions. |
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| Keywords: | Benzoates binding constant cobalt(III) coordination complexes one-pot synthesis X-ray crystallography |
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