Narrowing the gap: A compactly fused π‐conjugated molecule combines a high‐lying HOMO with a low‐lying LUMO (Eox−Ered=0.52 eV) and a fairly low‐lying LUMO+1 on the bridging unit, giving rise to strong optical charge‐transfer transitions. A facile electron transfer has been observed by EPR and NMR spectroscopies.

No abstract

In the search for transformations of quinone moieties into the corresponding tetracyano-p-quinodimethane (TCNQ) systems, Knoevenagel-type condensations of 2-thioxo-1,3-dithiole-p-benzoquinone systems, TTF-p-benzoquinone dyads and a p-benzoquinone-TTF-p-benzoquinone triad with malononitrile under different experimental conditions were investigated. In order to avoid the well-known Michael 1,4-addition onto the quinone moiety, cyclopentadiene or cyclohexadiene units were incorporated as protecting groups through [4+2] Diels-Alder cycloadditions. On the one hand, aromatization leading to fused 2-thioxo-1,3-dithiole-hydroquinones was observed in the presence of acetic acid and pyridine. With use, on the other hand, of the nucleophilic

Abstract-A new 1,3-dithiol-2-ylidene substituted naphthopyranone 2 has been synthesized and characterized. UV-vis spectroscopic and cyclic voltammetry results, interpreted on the basis of density functional theory, show that 2 displays an intramolecular charge-transfer transition and acts like a donor-acceptor (D-A) system. Furthermore, a weak fluorescence originating from the excited charge-transfer state is observed.

In the crystal structure of the title compound (systematic name: 2,3-dichloro­benzene-1,4-diol 2,3-dichloro­cyclo­hexa-2,5-diene-1,4-dione monohydrate), C6H4Cl2O2·C6H2Cl2O2·H2O, the 2,3-dichloro-1,4-hydro­quinone donor (D) and the 2,3-dichloro-1,4-benzoquinone acceptor (A) mol­ecules form alternating stacks along [100]. Their mol­ecular planes [maximum deviations for non-H atoms: 0.0133 (14) (D) and 0.0763 (14) Å (A)] are inclined to one another by 1.45 (3)° and are thus almost parallel. There are π–π inter­actions involving the D and A mol­ecules, with centroid–centroid distances of 3.5043 (9) and 3.9548 (9) Å. Inter­molecular O—H⋯O hydrogen bonds involving the water mol­ecule and the hy­droxy and ketone groups lead to the formation of two-dimensional networks lying parallel to (001). These networks are linked by C—H⋯O inter­actions, forming a three-dimensional structure.