Electronic Interactions in a New π-Extended Tetrathiafulvalene Dimer

• Published in: Chemistry : a European journal Vol. 12; no. 10; pp. 2709 - 2721
• Main Authors: Díaz, Marta C., Illescas, Beatriz M., Martín, Nazario, Perepichka, Igor F., Bryce, Martin R., Levillain, Eric, Viruela, Rafael, Ortí, Enrique
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 20.03.2006; WILEY‐VCH Verlag; Wiley
• Subjects: Anthracenes - chemistry; Chemistry; Chemistry, Multidisciplinary; cyclic voltammetry; density functional calculations; Dimerization; Electrochemistry; electron donors; Electronics; Heterocyclic Compounds - chemistry; Models, Chemical; Oxidation-Reduction; Physical Sciences; Science & Technology; spectroelectrochemistry; Stereoisomerism; tetrathiafulvalenes; POLARIZABLE CONTINUUM MODEL; BUILDING-BLOCKS; AB-INITIO; TTF; spectroelectrochemistry; REDOX PROPERTIES; MOLECULAR SADDLES; HARTREE-FOCK; electron donors; density functional calculations; cyclic voltammetry; RADICAL-CATION; RAY CRYSTAL-STRUCTURES; tetrathiafulvalenes; 9,10-BIS(1,3-DITHIOL-2-YLIDENE)-9,10-DIHYDROANTHRACENE DERIVATIVES
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.200501001

The first π‐extended tetrathiafulvalene (exTTF) dimer in which the two exTTF units are covalently connected by 1,3‐dithiole rings has been obtained in a multistep synthetic procedure involving the Ullmann cross‐coupling reaction by using copper(I) thiophene‐2‐carboxylate (CuTC). The electronic spectrum reveals a significant electronic interaction between the exTTF units. The electrochemical study carried out by cyclic voltammetry in solution and in thin‐layer conditions, and the electrochemical simulation and spectroelectrochemical (SEC) measurements confirm the electronic communication and show that the oxidation of dimer 14 occurs as two consecutive 2 e− processes D0–D0→D2+–D0→D2+–D2+. Theoretical calculations, performed at the B3P86/6‐31G* level, confirm the experimental findings and predict that 142+ exists as a delocalized D.+–D.+ species in the gas phase and as a localized D2+–D0 species in solution (CH3CN or CH2Cl2). Oxidation of 142+ forms the tetracation 144+ which is constituted by two aromatic anthracene units bearing four aromatic, almost orthogonal 1,3‐dithiolium cations. Se ha sintetizado el primer dímero derivado de TTF π‐extendido (exTTF) en el que las dos unidades de exTTF se encuentran unidas mediante un enlace covalente a través de los anillos de 1,3‐ditiol. El procedimiento sintético consta de varios pasos e implica una reacción de acoplamiento cruzado de tipo Ullmann empleando 2‐tiofencarboxilato de cobre(I) (CuTC). Los espectros electrónicos revelan una interacción electrónica significativa entre las unidades de exTTF. Se ha realizado el estudio electroquímico mediante voltamperometría cíclica en disolución y en condiciones de capa fina, así como la simulación electroquímica y las medidas espectroelectroquímicas. Los datos obtenidos confirman la comunicación electrónica entre ambas unidades, y muestran que la oxidación del dímero 14 ocurre como dos procesos que involucran dos electrones D0–D0 →D2+–D0→D2+–D2+. Cálculos teóricos B3P86/6‐31G* confirman los hechos experimentales y predicen que 142+ existe como una especie deslocalizada D.+–D.+ en fase gas y como una especie localizada D2+–sD0 en disolución (CH3CN o CH2Cl2). La oxidación de 142+ forma la especie tetracatiónica 144+, constituida por dos unidades de antraceno aromáticas con cuatro cationes 1,3‐ditiolio aromáticos en disposición prácticamente ortogonal a las unidades de antraceno. A dramatic change in conformation and a gain in aromaticity accompanies oxidation of the new π‐extended tetrathiafulvalene (exTTF) dimer 1. Electronic communication between the two exTTF units is revealed in a combined electrochemical, spectroscopic, and theoretical study. Oxidation involves two sequential 2e processes, D0–D0→D2+–D0→D2+–D2+, with inverted potentials on each exTTF moiety.