Thermodynamic and fluorescence emission studies on chemosensors containing anthracene fluorophores. Crystal structure of {[CuL1Cl]Cl}2·2H2O [L1 = N-(3-aminoprophyl)-N′-3-(anthracen-9-ylmethyl)aminopropylethane-1,2- diamine]

Ma Alexandra Bernardo, Fernando Pina, Beatriu Escuder, Enrique García-España, Maria Luz Godino-Salido, Julio Latorre, Santiago V. Luis, José A. Ramírez, Conxa Soriano

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Abstract

The co-ordination capabilities toward hydrogen ions, Co2+, Ni2+, Cu2+, Zn2+ and Cd2+ of the novel receptor 2,6,9,13-tetraaza[14](9,10)anthracenophane (L) and of its open-chain counterpart N-(3-aminopropyl)-N′-3-(anthracen-9-ylmethyl)aminopropylethane-1,2-diamine (L1) is described. Stepwise protonation constants of tne cyclic receptor (L) are lower than those of the open-chain receptor (L1). Quenching effects of the fluorescence emission occur upon first and second deprotonation of L and upon second deprotonation of L1. Stability constants of the Co2+, Ni2+, Cu2+, Zn2+ and Cd2+ complexes follow the Irving-Williams trend and are intermediate between those of triethylenetetraamine with terminal primary amino groups and those of the α,ω-dibenzylated receptor 1,12-dibenzyl-1,5,8,12-tetraazaciclododecane. Luminescence studies show that complexion of Cu2+ and Ni2+ by L1 yield CHEQ effects (chelation enhanced quenching) while complexation of Zn2+ and Cd2+ produce CHEF effects (chelation enhanced fluorescence). The magnitude of these effects depends on the strength of the co-ordination. Crystals of {[CuL1Cl]Cl}2· 2H2O are triclinic, space group P1, with a = 13.307(1), b = 13.305(1), c = 16.538(2) Å, a = 104.94(1), β = 111.67(1), γ = 102.76(1)°, R1 = 0.0885, wR2 = 0.2667. The crystal structure of {[CuL1Cl]Cl}2·2H2O shows a very strongly axially distorted square pyramidal co-ordination geometry in which the Cu2+ cation is co-ordinated by all the nitrogen donors of the receptor and a chloride ion disposed at the apical position of the square pyramid. The asymmetric unit is formed by two slightly different [CuL1Cl]+ cations with an arrangement that shows π-stacking of their anthracene sub-units.

Original languageEnglish
Pages (from-to)915-921
Number of pages7
JournalJournal of the Chemical Society - Dalton Transactions
Issue number6
DOIs
Publication statusPublished - 21 Mar 1999

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