Squaraine chemistry. A new approach to symmetrical and unsymmetrical photoconductive squaraines. Characterization and solid state properties of these materials

Abstract

A new approach to l-(p-dimethylaminophenyl)-2-hydroxycyclobutene-3,4-dione (4), a precursor for the synthesis of symmetrical and unsymmetrical photoconductive squaraines, is described. In situ generation of p-nitrophenyl ketene, by the reaction of p-nitrophenylacetyl chloride and triethylamine in the presence of tetraethoxyethylene in anhydrous ether, results in a (2+2) cycloaddition between the ketene and the electron-rich olefin. The cycloadduct generated, 6, was hydrolyzed to give 1-(p-nitropheny1)-2-hydroxycyclobutene-3,4-dione (5) in 51% yield. Reductive alkylation of 5 by hydrogen in the presence of formaldehyde in DMF at 50-60°C affords 4 in 81 % yield. The overall yield of 4 is 41 % from tetraethoxyethylene and is significantly better than other preparative procedures of 4 based on a partial Friedel-Crafts reaction or an arylation reaction of a squaric acid derivative with an aniline, where yields ranging from 8.5% to 24% were reported. Condensations of 4 with 2 equivalents of N, N-dimethylaniline and its derivatives in refluxing 2-propan01 in the presence of 6 equivalents of tributyl orthoformate yield symmetrical squaraine l a and unsymmetrical squaraines lb-le. The synthesis is accomplished by a (2+2) cycloaddition -reductive alkylation -condensation reaction sequence and represents a new, cost-effective synthesis for photoconductive squaraines where the expensive squaric acid reactant is bypassed. The spectroscopic and the solid state properties of la-le have been studied. Results show that the properties exhibited by l a -l e are essentially identical to those exhibited by other photoconductive, symmetrical squaraines that are synthesized by other known processes. From the resemblance in solid state properties, la-le are expected to be photoconductive. This has indeed been observed in preliminary experiments.KOCK-YEE LAW et F. COURT BAILEY. Can. J. Chem. 71,494 (1993) On dCcrit une nouvelle approche pour la preparation de la l-(p-dimethylaminophCnyl)-2-hydroxycyclobut~ne-3,4-dione (4), un precurseur dans la synthese de squarai'nes photoconductrices symetriques et non-symetriques. La generation in situ du p-nitrophknyl cetene, par la reaction du chlorure de p-nitrophCnylacetyle avec la triethylamine en presence de tCtraCthoxy6thylene dans l'ether anhydre, conduit 2 une cycloaddition (2+2) du c$t&ne et de l'olefine riche en electrons. L'hydrolyse du cycloadduit, 6, ainsi gCnerC conduit 2 la 1-(p-nitrophCny1)-2-hydroxycyclobut&ne-3-done (5) avec un rendement de 51%. L'alkylation reductrice de 5 par de l'hydrogene en presence de formaldehyde dans de DMF, a 50-60°C, fournit le composC 4 avec un rendement de 8 1 %. Le rendement global de 4 est de 41% B p a i r du tCtrakthoxy6thylene et ce rendement est supkrieur a ceux obtenus lors de preparations impliquant une reaction de Friedel-Crafts partielle ou une reaction d'arylation d'un derive de l'acide squarique avec de l'aniline alors que les rendements rapportks sont de l'ordre de 8,5 a 24%. Les condensations de 4 avec deux equivalents de N,N-dimethylanil...

Aggregation of Surfactant Squaraine Dyes in Aqueous Solution and Microheterogeneous Media: Correlation of Aggregation Behavior with Molecular Structure

“…The mixture was stirred and brought to reflux under nitrogen atmosphere. A solution containing 1-( p -dimethylaminophenyl)-2-hydroxycyclobutene-3,4-dione (previously prepared, 0.30 g, 1.38 mmol) in ∼2 mL of DMSO was added evenly through a pressure equalizing funnel over a 3-h period. The mixture was kept at reflux for an additional 2 h after the addition was completed.…”

Molecular Rods. 1. Simple Axial Rods

“…405 Unsymmetrical squaraines 212b are also accessible, as shown in Scheme 102. [406][407][408][409] For our purposes, aryl-and azulyl-substituted squaraines are modules for axial rods while other squaraines (e.g., bis(benzothiazolylidene)squa- raine) are modules for zigzag rods (cf. Part 2 19 ).…”

Synthesis, Characterization, Photophysics, and Photosensitization Studies of Squaraine−Bipyridinium Diads

“…4-N-Methyl-N-(3-bromopropyl)aminophenyl-4′-(N′,N′-dibutylamino)phenylsquaraine was prepared by condensing 1-(dibutylamino)phenyl-2-hydroxycyclobutene-3,4-dione (0.48 g, 1.6 mmol, synthesized according to the procedure of Chen et al 8 ) with N-methyl-N-(3-bromopropyl)aniline (0.34 g, 1.48 mmol) in the presence of tributylorthoformate (1 mL) in about 50 mL of 1-butanol at reflux for 2 h. 9 The progress of the synthesis was monitored by absorption spectroscopy. The product mixture was cooled in a refrigerator overnight.…”