Pilar de Miguel

Synthesis and intramolecular charge-transfer properties of new tetrathiafulvalene–σ-tetracyanoanthraquinodimethane diad (TTF–σ-TCNAQ) and triad (TTF–σ-TCNAQ–σ-TTF) molecules

We report the use of functionalised electron acceptor tetracyanoanthraquinodimethane (TCNAQ) units in the synthesis of novel diad D–σ-A compounds 6 and 7 [D=tetrathiafulvalenyl (TTF) and ferrocenyl] and the triad TTF–σ-TCNAQ–σ-TTF assembly 8. Compounds 6–8 display a very weak, broad, low-energy intramolecular charge-transfer band in the UV–VIS spectra. Nanosecond laser flash photolysis of compound 6 did not lead to any new transient absorptions in the 300–800 nm region, suggesting that if a charge-separated species is formed upon excitation, then back electron transfer occurs very rapidly to regenerate the ground state. Cyclic voltammetry of compounds 6–8 shows that reversible oxidation processes occur for the TTF and ferrocene moieties, and a reversible two-electron reduction occurs for the TCNAQ moiety. Spectroelectrochemical studies on compound 6 have enabled the redox processes to be assigned to the sequential formation of the TTF radical cation and dication upon oxidation, and the TCNAQ dianion upon reduction. Simultaneous electrochemistry and EPR (SEEPR) experiments provide further evidence for intramolecular interaction between the TTF and TCNAQ moieties in compound 6. Quantum mechanical calculations on compound 6, performed by the AM1 method, predict that in its minimum energy conformation the TTF and TCNAQ moieties are approximately orthogonal to one another, with the TCNAQ unit folded into a butterfly conformation.

Synthesis and Reactivity of β-Carboline-Hydantoin Systems

Abstract The synthesis of 2,5-disubstituted 1,3-dioxo-6H-1,2,3,5,11,11a-hexahydroimidazo[1, 5-b]-β-3a-y and the reduction of carbolines 3m-r with different amounts of lithium aluminium hydride is described.

Synthesis of 4-(4-pyridyl)oxazoles

Abstract Dimerization products and oxazoles have been synthesized from 4-acylaminomethyl-1-alkylpyridinium salts by heating with acetic anhydride at 100°C and 140°C respectively. One explanation is the formation of an anhydrobase as an intermediate; therefore, a new series of anhydrobase have been prepared to carry out the reaction, achieving a good synthetic procedure to obtain 4-(4-pyridyl)oxazoles.

Tricyanovinyithiophenes as novel electron acceptors for organic metals

The synthesis of novel tricyanovinylthiophenes 10 is reported; a structural solid state and electrochemical study proved their suitability as electron acceptors for organic metals.

Tetrafluoro and dichloro derivatives of thiophene-fused DCNQI- and TCNQ-type acceptors : a synthetic, electrochemical and crystallographic study

Novel thiophene-fused DCNQI derivatives8 and 11 bearing four fluorine atoms have been obtained in good yield from the corresponding quinones by reaction with bis(trimethylsilyl)carbodiimide (BTC). The presence of four fluorine atoms leads to good acceptor molecules which form charge transfer complexes in solution with N,N′-tetramethyl-p-phenylenediamine. The effect of chlorine atoms on the crystal packing in the analoguous thiophene-fused TCNQ derivatives 3a and 3b is also reported.