Crystal structure of mixed-ligand complexes of the Ni(II) heterospin bischelate withiso-butyl alcohol and 1,4-Butanediol

The crystal structures of the mixed-ligand complexes of the heterospin bischelate bis [2,2,5,5-tetramethyl-l-oxyl-3-imidazoline-4-(3’,3’,3’-trifluoro-1’-propenyl-2’-oxiato)nickel(II) (NiL₂) with iso-butanol and 1,4-butanediol NiL₂(i-C₄H₉OH)₂ and NiL₂[HO(CH₂)₄OH], respectively, are determined. The crystal structure of the NiL₂ complex with the normal butyl alcohol NiL₂(n-C₄H₉OH)₂ and the structure of CoL₂[HO(CH₂)₄OH] are refined. Translated fromZhurnal Strukturnoi Khimii, Vol. 38, No. 5, pp. 930–945, September-October, 1997.     

Problem of a wide variety of products in the Cu(hfac)2-nitroxide system

The stereochemically flexible Cu(hfac)(2) metal-ligand system when combined with polyfunctional nitroxides leads to a variety of solids with varying structure and composition. While investigating the products of Cu(hfac)(2) interaction with spin-labeled pyrazole 4,4,5,5-tetramethyl-2-(1-methyl-1H-pyrazol-4-yl)-imidazoline-3-oxide-1-oxyl, we have isolated a family of (12) heterospin compounds differing in structure and composition in the solid state. In synthetic systems, these compounds often cocrystallize and must be separated mechanically. It is also shown that minor variation of the structure of the solid heterospin complex can substantially change the magnetic properties of compounds.     

Bidentate-bridging butyleneglycol in a framework structure with A Co(II) mixed-ligand complex of an imidazoline nitroxyl

Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated from Zhurnal Strukturnoi Khimii, Vol. 33, No. 2, pp. 118–125, March–April, 1992.     

Molecular design of tautomeric interconversions of heterocycles

A classification and methodology of molecular design of ring—chain—ring (ring—ring) tautomeric systems by superposition of ring—chain equilibria in a structure of one molecule are considered.     

Synthesis, structure, and properties of a new representative of the family of calix[4]arene-containing [MnII 2MnIII 2]-clusters

A new representative of calix[4]arene-containing tetranuclear manganese complexes of the [Mn^II ₂Mn^III ₂] type was obtained. According to the data of magnetoochemical studies, the complex exhibits properties of molecular magnet at the temperature below 5 K. Parameters of the exchange interaction and the activation energy were determined. The influence of the peripheral environment on the magnetic properties of the tetranuclear manganese framework in the structure of the complex was revealed.     

The structure and magnetic properties of pyrazolyl-substituted benzimidazole-1-oxyl

The structure and magnetic properties of the benzimidazole-based nitronyl nitroxide radical containing pyrazole as a substituent in its side chain were studied.     

Copper(II) complexes with pyrazolyl-substituted nitronyl and imino nitroxides

It was established that the reactions of pyrazol-3-yl-substituted nitronyl nitroxide (HL¹) and pyrazol-3-yl-substituted imino nitroxide (HL³) with Cu(II) acetate lead to self-assembly of the Cu₄(OH)₂(OAc)₄(DMF)₂(L¹)₂ tetranuclear and Cu₂(OAc)₂(H₂O)₂(L³)₂ dinuclear complexes, respectively. The reaction of Cu(II) acetate with 5-ethoxycarbonyl-pyrazol-3-yl-substituted nitronyl nitroxide (HL²) gave unexpected solid Cu₂(H₂O)₂(L⁶)₂ · 2DMF, in which L⁶ is a deprotonated 5-carboxy-pyrazol-3-yl-substituted nitronyl nitroxide, formed as a result of cleavage of an ester bond in the starting HL². A similar transformation of the paramagnetic ligand was observed in the reaction of Cu(II) acetate with 5-ethoxycarbonyl-pyrazol-3-yl-substituted imino nitroxide (HL⁴). It led to the formation of Cu₂(DMF)₂(L⁷)₂, where L⁷ is deprotonated 2-(5-carboxy-1H-pyrazol-3-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole 3-oxide. An X-ray diffraction study indicated that in Cu₄(OH)₂(OAc)₄(DMF)₂(L¹)₂ and Cu₂(OAc)₂(H₂O)₂(L³)₂, the L¹ and L³ paramagnetic ligands perform the bridging cyclic tridentate function, while in Cu₂(H₂O)₂(L⁶)₂ · 2DMF and Cu₂(DMF)₂(L⁷)₂, the paramagnetic L⁶ and diamagnetic L⁷ are bridging bicyclic tetradentate ligands. The magnetic behavior of complexes with coordinated nitronyl nitroxide – Cu₄(OH)₂(OAc)₄(DMF)₂(L¹)₂ and Cu₂(H₂O)₂(L⁶)₂ · 2DMF is dictated by the dominant antiferromagnetic exchange interactions, which is confirmed by quantum-chemical data. The magnetic susceptibility of Cu₂(OAc)₂(H₂O)₂(L³)₂ reflects the competition between the antiferromagnetic and ferromagnetic components, of which the latter is due to electron coupling in the Cu(II) ← N=C–N ? O exchange channels. EPR data confirm the results received from static magnetic measurements for multispin solids.