Synthesis and photophysicochemical studies of non-metal 2,3,9,10,16,17,23,24-octacarboxyphthalocyanine

Abstract

A new method of preparation and the properties (solubility, aggregation, spectralluminescent properties, singlet oxygen and photobleaching quantum yields) of non-metal 2,3,9,10,16,17,23,24-octacarboxyphthalocyanine are reported. The influence of ionization state on photophysicochemical properties of this dye is also presented.

Synthesis of 4,5-Dicyanophthalic Acid and Its Functional Derivatives

“…Previously [31] we reported a method for preparation of 4,5-bis(ethoxycarbonyl)phthalonitrile by desymmetrization of pyromellitic anhydride 1. The key step in the synthesis Synthesis of 4,5-Dicyanophthalic Acid and its Functional Derivatives was the partial hydrolysis of tetraethyl pyromellitate to monoacid in aqueous ethanol [35] (Scheme 1).…”

“…4,5-Bis(ethoxycarbonyl)phthalonitrile was used for synthesis of OCPcM and OCPcH 2 . [31] We attempted to apply this method for synthesis of 4,5-bis(alkoxycarbonyl)phthalonitriles with other alkyl radicals (Me, Pr, Hx). Unfortunately, the partial trans-esterification occurred during the hydrolysis of tetraalkyl pyromellitates in aqueous ethanol at the second step with formation of mixture of esters.…”

“…To avoid this process we had to find the specific solvent system for each alkyl case depending on the solubility of starting tetraalkyl pyromellitates which was a significant drawback of the method. Target 4,5-bis(alkoxycarbonyl)-phthalonitriles were obtained from prepared 2,4,5-trialkyl pyromellitates by procedures similar to published in reference [31] with moderate to good yields (37, 67, 40 % for Me, Pr, Hx radicals starting from anhydride 1).…”

“…Tetramethyl and tetrapropyl pyromellitates were synthesized with quantitative yield from dianhydride 1 and corresponding trialkyl orthoformates according to [31,35] . (20 ml) and MeOH (5 ml) was treated dropwise with a solution of NaOH (0.23 g, 5.75 mmol) in water (3 ml) within 1.5 h. Stirring was continued for 2 h followed by evaporation of the solvent.…”

“…Only few examples of preparation of monomeric free ligand OCPcH 2 starting from 1,2,4,5-tetracyanobenzene in mild conditions with moderate yields are reported. [26,27] A much more attractive way which allows to obtain both metal complexes and free ligand and avoids formation of polymeric by-products is the tetramerization of 4,5-dicyanophthalic acid derivatives, mainly its alkyl esters [28][29][30][31] followed by hydrolysis if the acids are target compounds. Only a few reports on the synthesis of N-unsubstituted imide [32,33] and N,N-dialkylamides [33,34] of 4,5-dicyanophthalic acid were found in the literature.…”