title: Counter-ligand control of the electronic structure in dinuclear copper-tetrakisguanidine complexes.
abstract: The redox-active GFA (Guanidino-Functionalized Aromatic compound) 1,4,5,8-tetrakis(tetramethylguanidino)-naphthalene (6) is used to synthesize new dinuclear copper complexes of the formula [6(CuX2)2] with different electronic structures. With X = OAc, a dinuclear Cu(II) complex of the neutral GFA is obtained (electronic structure [Cu(II)-GFA-Cu(II)], two unpaired electrons), and with X = Br a diamagnetic dinuclear Cu(I) complex of the dicationic GFA (electronic structure [Cu(I)-GFA(2+)-Cu(I)], closed-shell singlet state). The different electronic structures lead to significant differences in the optical, structural and magnetic properties of the complexes. Furthermore, the complex [6(CuI)2](2+) (electronic structure [Cu(I)-GFA(2+)-Cu(I)], closed-shell singlet state) is synthesized by reaction of 6(2+) with two equivalents of CuI. Slow decomposition of this complex in solution leads to the fluorescent dye 2,7-bis(dimethylamino)-1,3,6,8-tetraazapyrene. In an improved synthesis of this tetraazapyrene, 6 is reacted with CuBr in the presence of dioxygen. Quantum chemical calculations show that the addition of counter-ligands to the trigonal planar Cu(I) atoms of [6(CuI)2](2+) favors or disfavors one of the electronic structures, depending on the nature of the counter-ligand.
authors.affiliation: Anorganisch-Chemisches Institut, Ruprecht-Karls Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany. hans-jorg.himmel@aci.uni-heidelberg.de.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Ziesak
authors.forename: Tobias
authors.initials: T
authors.lastname: Wesp
authors.forename: Olaf
authors.initials: O
authors.lastname: Hübner
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Kaifer
authors.forename: Hubert
authors.initials: H
authors.lastname: Wadepohl
authors.forename: Hans-Jörg
authors.initials: HJ
authors.lastname: Himmel
mesh_terms: D003300:Copper / Q000737:chemistry*; D003460:Crystallization; D018360:Crystallography, X-Ray; D005456:Fluorescent Dyes; D019791:Guanidine / Q000031:analogs & derivatives / Q000737:chemistry*; D008024:Ligands; D008280:Magnetics; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D012996:Solutions
chemical_list: D005456:Fluorescent Dyes; D008024:Ligands; D009942:Organometallic Compounds; D012996:Solutions; D003300:Copper; D019791:Guanidine; D010100:Oxygen