Solvent-Induced Change of Electronic Spectra and Magnetic Susceptibility of Co^II Coordination Polymer with 2,4,6-Tris(4-pyridyl)-1,3,5-triazine

Abstract

One-dimensional coordination polymer [Co(Piv)2(4-ptz)(C2H5OH)2]n (compound 1, Piv(-) = pivalate, 4-ptz = 2,4,6-tris(4-pyridyl)-1,3,5-triazine) was synthesized by interaction of Co(II) pivalate with 4-ptz. Desolvation of 1 led to formation of [Co(Piv)2(4-ptz)]n (compound 2), which adsorbed N2 and H2 at 78 K as a typical microporous sorbent. In contrast, absorption of methanol and ethanol by 2 at 295 K led to structural transformation probably connected with coordination of these alcohols to Co(II). Formation of 2 from 1 was accompanied by change of color of sample from orange to brown and more than 2-fold decrease of molar magnetic susceptibility (χM) in the temperature range from 2 to 300 K. Resolvation of 2 by ethanol or water resulted in restoration of spectral characteristics and χM values almost to the level of that of 1. χMT versus T curves for 1 and samples, obtained by resolvation of 2 by H2O or C2H5OH, were fitted using a model for Co(II) complex with zero-field splitting of this ion.

CoIIComplexes with a Tripyridine Ligand, Containing a 2,6-Di-tert-butylphenolic Fragment: Synthesis, Structure, and Formation of Stable Radicals

“…Co–O, Co–N, and Co–Cl bond lengths are typical for Co II complexes with octahedral and tetrahedral coordination environments. 12,29,33 As in the case of 1 , ligand L is bridging and links Co1 and Co2 (or Co2′) ions. The neighboring molecules of 3 are bound by hydrogen bonds with participation of the coordinated H 2 O from one molecule of 3 and Cl – anions from the another one; however, no signs of π-stacking could be found in this case.…”

“…Coordination polymers are considered as the basis for creation of new sorbents, catalysts, and luminescent and magnetic materials. 1−5 The specific feature of such systems is their capacity to combine several physical properties, which can find application in practice, such as nontrivial magnetism and luminescence, 6−8 catalytic activity along with the ability to adsorb certain substrates, 9−11 and the ability to change the physical property upon interaction with different compounds 7,12,13 or action of external factors (irradiation, pressure, etc.). 14−17 For creation of materials with tunable properties, metal–radical complexes are promising objects because free radical generation or disappearance can make significant influence on electric conductivity 18,19 and can be an instrument for luminescence control.…”

Field-Induced Single-Ion Magnet Behaviour in Two New Cobalt(II) Coordination Polymers with 2,4,6-Tris(4-pyridyl)-1,3,5-triazine

“…Though similar Co II complexes based on a TPT ligand with a zigzag chain structure have been reported in the literature [23,24], the dynamic magnetic properties of these chains have never been studied. High magnetic anisotropy was revealed in the compound [Co(Piv) 2 (TPT)(C 2 H 5 OH) 2 ] n (CoPiv) by Eremenko and co-workers, which showed a spin state switching after desolvation [23]. Complex 2 crystallises in the monoclinic space group C2/c and the Co II centre is also in a distorted octahedral geometry with a N 2 O 4 coordination environment, where the N and O atoms are provided by the TPT ligands, coordinated water molecules, and formate groups, respectively ( Figure S3 and Figure 2c).…”

“…As for compound 2, it has a 1D chain structure bridged by two of the three pyridines of the TPT ligand ( Figure 2d). Though similar Co II complexes based on a TPT ligand with a zigzag chain structure have been reported in the literature [23,24], the dynamic magnetic properties of these chains have never been studied. High magnetic anisotropy was revealed in the compound [Co(Piv)2(TPT)(C2H5OH)2]n (CoPiv) by Eremenko and co-workers, which showed a spin state switching after desolvation [23].…”

2D Coordination Polymer Built from Lithium Dimethylmalonate and CoII Ions: The Influence of Dehydration on Spectral and Magnetic Properties

“…Change of dimensionality induced by adsorption or desorption of guest molecules can lead to a change of magnetic phase transition temperature at low temperatures (as a rule, below 120 K) . In contrast, a change of the coordination environment of a metal ion can lead to the occurrence of another spin state or change of spin–orbit coupling (SOC) contribution, and such effects can be detected at room temperature , . The latter possibility seems to be especially attractive, because the majority of potential guest molecules that are interesting for modern technology can be efficiently absorbed or desorbed at relatively high temperatures (usually, close to room temperature), and the associated changes of magnetic properties should occur in a similar temperature range.…”