Sorption and Magnetic Properties of Oxalato-Based Trimetallic Open Framework Stabilized by Charge-Assisted Hydrogen Bonds

• Published in: International journal of molecular sciences Vol. 23; no. 3; p. 1556
• Main Authors: Muzioł, Tadeusz Mikołaj, Tereba, Natalia, Podgajny, Robert, Pełka, Robert, Czernia, Dominik, Wiśniewski, Marek, Koter, Stanisław, Wrzeszcz, Grzegorz
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 29.01.2022; MDPI
• Subjects: Acetonitrile; Adsorbed water; Adsorption; Antiferromagnetism; Bonding strength; Bromobenzene; Cell size; charge assisted hydrogen bonds; Cobalt; coordination polymer; Coordination polymers; Crystallization; Dimerization; Hydrogen Bonding; Hydrogen bonds; Ligands; Magnetic Phenomena; Magnetic properties; Metals - chemistry; Models, Molecular; Molecular Conformation; Nitrogen; Occupancy; oxalate complex; Oxalates - chemistry; Oxalic acid; Porous materials; Potassium; single crystal XRD; Solvents; sorption properties; Spectrophotometry, Infrared; Spectroscopy, Fourier Transform Infrared; Structural stability; Temperature; Topology; Water - chemistry; X-Ray Absorption Spectroscopy; charge assisted hydrogen bonds; single crystal XRD; sorption properties; oxalate complex; magnetic properties; coordination polymer
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms23031556

We report a new structure of {[Co(bpy) (ox)][{Cu (bpy) (ox)}Fe(ox) ]} ·8.5nH O presenting a rare ladder topology among oxalate-based coordination polymers with anionic chains composed of alternately arranged [Cu (bpy) (ox)] and [Fe(ox) ] moieties. Along the a axis, they are separated by Co(III) units to give porous material with voids of 963.7 Å (16.9% of cell volume). The stability of this structure is assured by a network of stacking interactions and charge-assisted C-H…O hydrogen bonds formed between adjacent chains, adjacent cobalt(III) units, and alternately arranged cobalt(III) and chain motifs. The soaking experiment with acetonitrile and bromobenzene showed that water molecules (8.5 water molecules dispersed over 15 positions) are bonded tightly, despite partial occupancy. Water adsorption experiments are described by a D'arcy and Watt model being the sum of Langmuir and Dubinin-Serpinski isotherms. The amount of primary adsorption sites calculated from this model is equal 8.2 mol H O/mol, being very close to the value obtained from the XRD experiments and indicates that water was adsorbed mainly on the primary sites. The antiferromagnetic properties could be only approximately described with the simple Cu -ox-Cu dimer using = - · · , thus, considering non-trivial topology of the whole Cu-Fe chain, we developed our own general approach, based on the semiclassical model (SC) and molecular field (MF) model, to describe precisely the magnetic superexchange interactions in . We established that Cu(II)-Cu(II) coupling dominates over multiple Cu(II)-Fe(III) interactions, with = -275(29) and = -3.8(1.6) cm and discussed the obtained values against the literature data.