Reversible Dimerization and Polymerization of a Janus Diradical To Produce Labile C-C Bonds and Large Chromic Effects.

Conducting polymers can be synthesized by irreversible diradical monomer polymerization. A reversible version of this reaction consisting of the formation/dissociation of σ-dimers and σ-polymers from a stable quinonoidal diradical precursor is described. The reaction reversibility is made by a quinonoidal molecule which changes its structure to an aromatic species by forming weak and long intermolecular C-C single bonds. The reaction provokes a giant chromic effect of about 2.5 eV. The two opposite but complementary quinonoidal and aromatic tautomers provide the Janus faces of the reactants and products which produces the observed chromic effect. A reaction mechanism is proposed to explain the variety of final products starting with structurally very similar reactants. These reversible reactions, covering an unusual regime of weak covalent supramolecular bonding, yield products which might be envisaged as novel molecular and polymeric soft matter phases.

Quinoidal naphtho[1,2-b:5,6-b']dithiophenes for solution-processed n-channel organic field-effect transistors.

A series of new quinoidal naphthodithiophenes, 2,7-bis(α,α-dicyanomethylene)-2,7-dihydronaphtho[1,2-b:5,6-b']dithiophenes, in which all the four fused aromatic rings are incorporated into the quinoidal system, were synthesized and evaluated as an n-channel organic semiconductor. Solution-processed field-effect transistors exhibited typical n-channel transistor characteristics with the mobility as high as 0.1 cm(2) V(-1) s(-1), which is higher by more than 1 order of magnitude than those reported for isomeric quinoidal naphthodithiophenes having a naphthoquinoidal structure.

Dithiophene-Fused Tetracyanonaphthoquinodimethanes (DT-TNAPs): synthesis and characterization of π-extended quinoidal compounds for n-channel organic semiconductor.

Dithiophene-fused tetracyanonaphthoquinodimethanes (DTTNAPs) were synthesized and evaluated as n-channel organic semiconductors. DTTNAPs, regardless of isomeric structures and substituents, have low-lying LUMO energy levels (∼4.6 eV below the vacuum level), suitable for stable n-channel field-effect transistors (FETs) under ambient conditions. In fact, α-DTTNAP derivatives afforded solution-processed FETs showing an electron mobility of 10(-3) cm(2) V(-1) s(-1), indicating that DTTNAPs are a potential molecular framework for n-channel organic semiconductors.

Orthogonally functionalized naphthodithiophenes: selective protection and borylation.

Selective functionalization protocols of naphtho[1,2-b;5,6-b']dithiophene (NDT3) by combining protection of the thiophene α-positions and direct borylation on the naphthalene core are described, which allows synthesizing a number of new NDT3-based building blocks with various substituents and isomeric NDT3-based polymers with different main chain structures. The same protocol is applicable to other isomeric naphthodithiophenes (NDTs), which affords a set of key building blocks for the development of elaborated functional π-materials.