Porphyrin-like macrocyclic complexes: molecular and electronic structure of (5,14-dihydro-6,8,15,17-tetramethyldibenzo[b,i][1,4,8,11]tetraazacyclotetradecinato)copper(II)

Abstract

Reaction of equimolar amounts of Li₂(tmtaa)(H₂tmtaa = 5,14-dihydro-6,8,15,17-tetramethyldibenzo[b,i][1,4,8,11]tetraazacyclotetradecine) with Cu(O₂CMe)₂ afforded the [Cu(tmtaa)] complex in > 98% yield. Single-crystal X-ray diffraction studies have shown that the structure of [Cu(tmtaa)] is monoclinic, space group P2₁/c, with a= 14.332(1), b= 16.443(2), c= 16.313(2)Å, β= 100.03(1)° and Z= 8. The complex exhibits the usual saddle-shaped geometry reported for this ligand. The average Cu–N distance is 1.929 Å and the displacement of the copper centre out of the N₄ plane is only 0.070 Å. The electronic structure of the complex has been established by combined ultraviolet photoelectron spectroscopy and density functional calculations. The relevant features of the metal–ligand interaction are typical of porphyrin-like copper tetraazamacrocycles.