Synthesis and properties of substituted (p-aminostyryl)-1-(3-sulfooxypropyl)pyridinium inner salts as a new class of two-photon pumped lasing dyesElectronic supplementary information (ESI) available: synthesis details for compounds 7b, 7c, 8b and 8c. See http://www.rsc.org/suppdata/jm/b3/b307504d/

A series of substituted (p-aminostyryl)-1-(3-sulfooxypropyl)pyridinium (ASSP) inner salts have been synthesized and characterized. For comparison purposes substituted (p-aminostyryl)pyridinium iodide (ASPI) salts and substituted (p-aminostyryl)pyridinium tosylate (ASPT) salts were also prepared. Their linear absorption, two-photon absorption and emission properties have been studied. All these dyes exhibit relatively large two-photon absorption (TPA) cross-section values at a wavelength of 1064 nm. When pumped by a 1064 nm IR laser beam, two-photon pumped (TPP) frequency up-conversion lasing was observed in all these dyes, except for trans-4-{p-[N-methyl-N-(2-acetic acid ethyl ester)amino]styryl}-1-methylpyridinium tosylate (8b). The TPP lasing peaks of these dyes range from 612 nm to 637 nm, with half bandwidths varying from 2 nm to 11 nm. Compared with the substituted ASPI salts or the substituted ASPT salts, the substituted ASSP inner salts show enhanced TPP lasing. The TPP lasing efficiency of the trans-4-{p-[N-ethyl-N-(2-hydroxyethyl)amino]styryl}-1-(3-sulfooxypropyl)pyridinium inner salt (6e) is as high as 27%.