title: Thiophene-benzoquinones: synthesis, crystal structures and preliminary coordination chemistry of derived anilate ligands.
abstract: 2,5-Bis(thiophene) and 2,5-bis(ethylenedioxy-thiophene) (EDOT) derivatives of 3,6-diethoxy-1,4-benzoquinone (para isomers) were prepared by Stille coupling between the 2,5-dibromo-3,6-diethoxy-1,4-benzoquinone precursors and (n-Bu)3Sn-R (R = 2-thiophenyl or 3,4-ethylenedioxy-2-thiophenyl) reagents. In a parallel series of experiments 2,6-bis(thiophene) and 2,6-EDOT-3,5-diethoxy-1,4-benzoquinone (meta isomers) were synthesized by the same strategy. The four compounds were structurally characterized. The thiophene derivatives show essentially planar conformation thanks to the conjugation and establishment of S···O 1,5-nonbonded interactions, while in the EDOT derivatives the thiophene moieties are twisted with respect to the benzoquinone ring because of the steric hindrance. TD-DFT calculations were performed on both para and meta thiophene isomers in order to explain the differences observed in the UV-Vis absorption spectra. The 2,5-derivatives are valuable precursors for thiophene containing anilate (An) ligands, as the first examples of electron rich substituent based anilates. The Cu(II) complex [Cu(Th2An)(tbbpy)]·2H2O (Th2An = thiophene-anilate; tbbpy = 4,4'-bis(tert-butyl)-2,2'-bipyridine) was isolated and structurally characterized. The metal center lies within a square planar coordination geometry, while the ligands engage in a set of intermolecular contacts.
authors.affiliation: Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Cagliari, S.S. 554 - Bivio per Sestu, I09042 Monserrato (Cagliari), Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Atzori
authors.forename: Flavia
authors.initials: F
authors.lastname: Pop
authors.forename: Thomas
authors.initials: T
authors.lastname: Cauchy
authors.forename: Maria Laura
authors.initials: ML
authors.lastname: Mercuri
authors.forename: Narcis
authors.initials: N
authors.lastname: Avarvari
mesh_terms: D015082:2,2'-Dipyridyl / Q000737:chemistry*; D016227:Benzoquinones / Q000138:chemical synthesis*; D002413:Cations, Divalent; D056831:Coordination Complexes / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004583:Electrons; D008024:Ligands; D008958:Models, Molecular; D008968:Molecular Conformation; D011789:Quantum Theory; D013237:Stereoisomerism; D013876:Thiophenes / Q000138:chemical synthesis*
chemical_list: D016227:Benzoquinones; D002413:Cations, Divalent; D056831:Coordination Complexes; D008024:Ligands; D013876:Thiophenes; D015082:2,2'-Dipyridyl; D003300:Copper