Pyrromethene–BF₂ complexes as laser dyes:1.

Abstract

Condensations between 3‐X‐2,4‐dimethylpyrroles (X = H, CH3, C2H5, and CO2C2H5) and acyl chlorides gave derivatives of 3,5,3′,5′‐tetramethylpyrromethene (isolated as their hydrochloride salts): 6‐methyl, 6‐ethyl, 4,4′,6‐trimethyl, 4,4′‐diethyl‐6‐methyl, and 4,4′‐dicarboethoxy‐6‐ethyl derivatives for conversion on treatment with boron trifluoride to 1,3,5,7‐tetramethylpyrromethene–BF2 complex (TMP–BF2) and its 8‐methyl (PMP–BF2), 8‐ethyl, 2,6,8‐trimethyl (HMP–BF2),2,6,‐diethyl‐8‐methyl (PMDEP–BF2), and 2,6‐dicarboethoxy‐8‐ethyl derivatives. Chlorosulfonation converted, 1,3,5,7,8‐pentamethylpyrromethene–BF2 complex to its 2,6‐disulfonic acid isolated as the lithium, sodium (PMPDS–BF2), potassium, rubidium, cesium, ammonium, and tetramethylammonium disulfonate salts and the methyl disulfonate ester. Sodium 1,3,5,7‐tetramethyl‐8‐ethylpyrromethene‐2,6‐disulfonate–BF2 complex was obtained from the 8‐ethyl derivative of TMP–BF2. Nitration and bromination converted PMP–BF2 to its 2,6‐dinitro‐(PMDNP–BF2) and 2,6‐dibromo‐ derivatives. The time required for loss of fluorescence by irradiation from a sunlamp showed the following order for P–BF2 compounds (10−3 to 10−4 M) in ethanol: PMPDS–BF2, 7 weeks; PMP–BF2, 5 days; PMDNP–BF2, 72 h; HMP–BF2, 70 h; and PMDEP–BF2, 65 h. Under similar irradiation PMPDS–BF2 in water lost fluorescence after 55 h. The dibromo derivative was inactive, but each of the other pyrromethene–BF2 complexes under flashlamp excitation showed broadband laser activity in the region λ 530–580 nm. In methanol PMPDS–BF2 was six times more resistant to degradation by flashlamp pulses than was observed for Rhodamine‐6G (R‐6G). An improvement (up to 66%) in the laser power efficiency of PMPDS–BF2 (10−4 M in methanol) in the presence of caffeine (a filter for light <300 nm) was dependent on flashlamp pulse width (2.0 to 7.0 μsec).

Photophysics of BODIPY Dyes as Readily-Designable Photosensitisers in Light-Driven Proton Reduction

“…All solutions and liquids in multicomponent catalyst systems were degassed via ultrasound treatment for at least 30 min before use. BODIPY dyes 1 [37], 2 [38], 3 [26], 4 [39], 5, 7, 8 [40], and 6 [41] were prepared using published procedures.…”

Efficient Radiative Pumping of Polaritons in a Strongly Coupled Microcavity by a Fluorescent Molecular Dye

“…As the active optical material, we have used the molecular dye BODIPY-Br [bromine substituted boron-dipyrromethene] (a variant upon the dipyrromethene family) as shown in Figure 1. BODIPY and its variants are noted for their high photoluminescence quantum yield (PLQY), narrow absorption and emission lines, broad solvent compatibility, low triplet-state formation, and high thermal and photochemical stability [41] and have been used as a biological labels [42] and as laser dyes [43] . Importantly, BODIPY-derivatives are known to undergo  stacking, with a co-existence between uncoupled monomers, weakly-emissive H-aggregates and J-aggregate-dimers that co-exist within molecular films at high concentration [30][31][32] .…”

Synthesis of 2,6-diethyl-3-methacroyloxymethyl-1,5,7,8-tetramethylpyrromethene-BF2 for the preparation of new solid-state laser dyes

“…It was interesting to note that comparison of the fluorescence quantum yields for the pyrromethene-BF 2 derivatives 1 (U 0.83) [1], 5 (U 0.12) [8], 7 (U 0.70) [8], and 2 (U 0.59) correlated well with the electron-withdrawing nature associated with the substituent on C(3) of the pyrromethene-BF 2 nucleus. The greater the electronwithdrawing ability of the C(3)-substituent, the lower was the fluorescence quantum yield.…”

“…The synthesis of the monomeric pyrromethene-BF 2 unit 2 was envisaged to proceed from 1 using methodology previously developed in these laboratories [1]. The preparation of 1 was achieved in straightforward fashion using slightly modified experimental conditions.…”

“…The pyrromethene-BF 2 complex dye molecules have been shown to possess laser performances that are superior to that of rhodamine-6G [1,2]. In 1993, 2,6-diethyl-1,3,5,7,8-pentamethylpyrromethene-BF 2 complex (1, DEPMP-BF 2 ) was found to exhibit twice the power efficiency of rhodamine-6G.…”