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)

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.