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

Abstract

We report a new structure of {[Co(bpy)2(ox)][{Cu2(bpy)2(ox)}Fe(ox)3]}n·8.5nH2O NCU-1 presenting a rare ladder topology among oxalate-based coordination polymers with anionic chains composed of alternately arranged [Cu2(bpy)2(ox)]2+ and [Fe(ox)3]3- moieties. Along the a axis, they are separated by Co(III) units to give porous material with voids of 963.7 Å3 (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 H2O/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 CuII-ox-CuII dimer using H = −J×S1×S2, 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 NCU-1. We established that Cu(II)-Cu(II) coupling dominates over multiple Cu(II)-Fe(III) interactions, with JCuCu = −275(29) and JCuFe = −3.8(1.6) cm−1 and discussed the obtained values against the literature data.

New Dinuclear Macrocyclic Copper(II) Complexes as Potentially Fluorescent and Magnetic Materials

“…In the case of the L 3 edge, they occurred at 931.0 and 934.8 eV for K1 and 931.0 and 934.7 eV for K2, and the L 2 features were shifted by around 20 eV towards higher energies. Those values were common for Cu(II) compounds [55][56][57]. According to the theory, the intensity of L 3 peaks was around twofold stronger than in the case of L 2 , and only one peak related to 2p→3d transitions was expected [58][59][60].…”

Influence of neutral auxiliary ligands on crystal structure and magnetic behaviour of new [MnII2MnIII2] clusters supported by p-adamantylcalix[4]arene

“…In recent decades, there has been a growing interest in the synthesis of new organic polydentate ligands capable of promoting a relatively strong magnetic response of paramagnetic metal ions, which can be achieved by controlling their coordination sphere distortion, offering a wide range of potential applications as smart materials. [1][2][3][4][5][6][7][8][9][10] In particular, the design of new single-molecule magnetic compounds, 11 which can retain their magnetization without a magnetic field and exhibit hysteresis below a certain temperature, through organic synthesis is a highly challenging scientific area. The focus has been on the development of new computing technologies, 12 exploiting the quantum principles of data storage and operation.…”