Mononuclear, hexanuclear and polymeric indium(iii) pyrazolido complexes; structural characterization, dynamic solution studies and luminescent properties

Abstract

A new family of six mononuclear indium(III) complexes of formula mer-[In^IIICl₃(pz*H)₃]—pz*H = pyrazole (pzH), or substituted pyrazoles: 4-Cl-pzH, 4-Br-pzH, 4-I-pzH, 4-Ph-pzH and 3,5-Me₂-pzH—were synthesized by addition reactions of InCl₃ and pz*H and crystallographically characterized. The fluxional behaviour of the complexes, probed by variable temperature ¹H NMR spectroscopy in the 328 K to 173 K range, was attributed to (at least) four simultaneous processes: pyrazole N–H proton dissociation/association, cis/trans-pyrazole exchange, and N¹/N² tautomerization of the cis- and of the trans-pyrazoles. Three novel trianionic hexanuclear complexes of general formula (pipH)₃[In₆Cl₆(μ₃-OH_0.5)₂(μ-OH)₆(μ-pz*)₆]—pz* = pz, 4-Cl-pz and 4-Ph-pz—showing μ-hydroxo and μ-oxo bridges were synthesized from the corresponding mer-[In^IIICl₃(pz*H)₃] and characterized by single crystal X-ray diffraction and ¹H NMR. Under different solvent conditions, multicolour emitting polymeric complexes of general formula [In(μ-pz*)₃]_n—pz* = pz, 4-Cl-pz, 4-I-pz and 4-Ph-pz—were obtained also from mer-[In^IIICl₃(pz*H)₃] after addition of a base. Luminescence and lifetime calculations were performed for all polymers formed.