Pseudohalide copper(II) complexes derived from polypyridyl ligands: Synthesis and characterization

A novel series of pseudohalide- (N3- NCS−) and perchlorato–Cu(II) complexes possessing a series of ligands with pyridyl-containing donors have been investigated. These include [Cu(pmap)ClO4)]ClO4 (1), [Cu(pmap)(N3)]ClO4 (2), [Cu(pmea)(N3)]ClO4·H2O (3), [Cu(dp-pa)(N3)]ClO4·½H2O (4), [Cu(pzdepy)ClO4]ClO4 (5), [Cu(pzdepy)(NCS)]ClO4 (6) and [Cu2(L)(NCS)4]·2CH3CN (7) where pmap = bis[2-(2-pyridylethyl)]-(2-pyridylmethyl)amine, pmea = bis(2-pyridylmethyl)-2-(2-pyridylethyl)amine, dp-pa = N-propanamide-N,N-bis(2-pyridylmethyl)amine, pzdepy = N,N′-bis[2-(2-pyridylethyl)]piperazine and L = 3,5-bis[bis(2-pyridylmethyl)aminomethyl]-toluene. All complexes were characterized by elemental analyses, IR and UV–Visible spectroscopy. The visible spectra of all complexes reveal the square-pyramidal geometries (SP) around the central Cu2+ ion. IR spectra confirmed the coordination of the ClO4- group in 1 and 5 and the N-donor thiocyanate group in complexes 6 and 7. The X-ray structure determination of the pseudohalide complexes 2, 6 and 7 confirmed the monodentate coordination nature of N3- and NCS− ions. The structure of 2 or 6 consists of isolated [Cu(pmap)(N3)]+ or [Cu(pzdepy)(NCS)]+ cations and perchlorate counter anions. The copper centers are penta-coordinated by the four N atoms of the pmap or pzdepy and N(5) atom of the azide group in 2 and the thiocyanate group in 6. In the dinuclear unit [Cu2(L)(NCS)4] of 7, each copper atom forms bonds to three nitrogen atoms of the ligand L, [CuN bonds from 2.013(2) to 2.054(2) Å], and to N(4) and N(5) atoms of the two terminal thiocyanato groups [Cu(1)N(4) = 1.954(2) Å; Cu(1)N(5) = 2.178(2) Å]. The intradimer Cu(1)...Cu(1A) distance is 5.7010(14) Å. An intramolecular π–π stacking with a ring–ring separation of 3.5991(14) Å is observed between the central benzene ring and the pyridyl rings. In the three complexes (2, 6 and 7), the CuN5 chromophore may be described as an axially elongated square pyramid.