Construction of copper chains with new fluorescent guanidino-functionalized naphthyridine ligands. Issue 42 (3rd October 2016)

• Record Type: Journal Article
• Authors: Krämer, Christoph; Leingang, Simone; Hübner, Olaf; Kaifer, Elisabeth; Wadepohl, Hubert; Himmel, Hans-Jörg
• Is Part Of: Dalton transactions. Volume 45:Issue 42(2016)
• Page Start: 16966
• Page End: 16983
• Publication Date: 2016-10-03
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c6dt03166h
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : A high charge and a low coordination number are the characteristics of fluorescent Cu4 chain complexes with 2, 7-bisguanidino-naphthyridine ligands. Abstract : The three new blue-fluorescent ligands 2, 7-bis(tetramethylguanidino)-1, 8-naphthyridine (1 ), 2, 7-bis( N, N ′-dimethylethylene-guanidino)-1, 8-naphthyridine (2 ) and 2, 7-bis( N, N ′-diisopropylguanidino)-1, 8-naphthyridine (3 ) are synthesized, and their optical properties (electronic absorption and emission spectroscopy) studied. Reactions of1 or2 with [Cu(CH3 CN)4 ]BF4 yield the Cu4 chain compounds [Cu4 (1 )2 ](BF4 )4 (that crystallizes as [Cu4 (1 )2 (CH3 CN)2 ](BF4 )4 ·2CH2 Cl2 ) and [Cu4 (2 )2 ](BF4 )4 . The variations of the optical properties upon coordination are evaluated, and the electronic transitions identified by time-dependent DFT (TD-DFT) calculations. Then the redox properties of the new Cu4 chain complexes are studied. In the course of these experiments, the new Cu6 complex [Cu4 (1 )2 (CuCl2 )2 ] 2+, in which two CuCl2 − units coordinate to the Cu4 chain in [Cu4 (1 )2 ] 4+, was fully characterized. In addition, the Cu3 chain complexes [Cu3 (1 )3 ] 3+ and [Cu3 (1 )2 ] 3+ were isolated as products of redox-induced degradation processes. Finally, we show by quantum chemical calculations that in [M4 (1 )2 ] 4+ complexes (M = coinage metal), the HOMO changes from a ligand-centered to a metal-centered orbital for replacement of M = Cu by Au.