Synthesis, structural and magnetic characterisation oftris(1-methyl-4,5-diphenylimidazol-2-yl)methanol (L) and[{CuL(NO3)}2][NO3]2

Tris(1-methyl-4,5-diphenylimidazol-2-yl)methanol (L) has been synthesized and characterised. It crystallises as L·0.5 1,2-Cl 2 C 2 H 4 from 1,2-Cl 2 C 2 H 4 –light petroleum and its crystal structure has been determined. This compound reacts with Cu(NO 3 ) 2 ·3H 2 O to yield [{CuL(NO 3 )} 2 ][NO 3 ] 2 which has also been crystallographically characterised. Each [{CuL(NO 3 )} 2 ] 2+ is located on a crystallographic inversion centre; the N 2 O 3 co-ordination sphere has a geometry intermediate between square pyramidal and trigonal bipyramidal, with a slight bias towards the former. The Cu(1)–O(1)–Cu(1*) bridging angle is small at 95.1(2)° and the Cu ··· Cu separation of 3.011(1) A is typical of a coplanar-type di-µ-oxo-copper(II) dimer. Magnetic susceptibility (300–4 K) measurements indicated that the dimeric complex has a spin-triplet ground state, i.e. the two copper(II) ions are ferromagnetically coupled. Variable-temperature (300–4 K) EPR spectroscopy confirmed an S = 1 ground state described by the spin-Hamiltonian parameters g xx = 2.09, g yy = 2.08, g zz = 2.24, |D| = 0.35 cm -1 and |E| = 0.049 cm -1 at room temperature. The magnitude of the zero-field splitting parameter |D| and the value of 2J decrease with decreasing temperature.

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