Luminescent Dipyrrinato Complexes of Trivalent Group 13 Metal Ions

Abstract

Although free dipyrrins (dipyrromethenes) do not strongly luminesce, certain dipyrrinato complexes of BF2 and zinc(II) are known to be intensely luminescent species. Two new dipyrrinato fluorophores, based on complexes with gallium(III) and indium(III), are described. Using a previously described meso-mesityl-substituted dipyrrin, namely 5-mesityldipyrrin (mesdpm), the complexes [Ga(mesdpm)3] and [In(mesdpm)3] were prepared and structurally characterized. The complexes display the expected octahedral geometry about the metal ions. In some solvents, such as hexanes, the complexes emit green light upon excitation with UV light at room temperature, with quantum yields of 2.4% ([Ga(mesdpm)3]) and 7.4% ([In(mesdpm)3]) and lifetimes in the low nanosecond range. Observations are consistent with assignment to ligand-localized transitions, and this interpretation is further confirmed by density functional calculations described herein. The new complexes are important additions to the widely used family of dipyrrin-based fluorescent species and show that dipyrrinato complexes containing metals other than BF2 and zinc(II) may be useful fluorophores.

New luminophors based on the binuclear helicates of d-METALS with BIS(DIPYRRIN)S

“…2), prepared from 5-mesityldipyrrin, was highly fluorescent with multinanosecond singlet excited-state lifetime [13]. Homoleptic Ga(III) and In (III) analogues of 5 exhibit less intense fluorescence (Φ f in hexanes 0.024 and 0.074 respectively) [14]. complexes [13,14].…”

“…Homoleptic Ga(III) and In (III) analogues of 5 exhibit less intense fluorescence (Φ f in hexanes 0.024 and 0.074 respectively) [14]. complexes [13,14].…”

“…The quantum yield of photodestruction process in cyclohexane (Φ photo ) in 4-5 times higher than that in ethanol (Table 5). [13,14].…”

“…rescence of the complexes [Zn 2(11) 2 ]-[Zn 2(14) 2 ] in ethanol and cyclohexane on the temperature was investigated[53]. The fluorescence intensity of [Zn 2 L 2 ] complexes in frozen (77 K) cyclohexane is retained the same as at room temperature with a slight blue shift (5-8 nm) of the emission band.…”

A Tetrakis(tetrazolyl) Analogue of EDTA

“…The intuitive presumption that incorporation of the N-H "acidic" nitrogen atom into an extended π system would appreciably lower the pK a does not hold. For example, "monoacidic" dipyrrins [10] have received growing attention as anionic N ligands, particularly for BODIPYderived dye development, [11,12] but they still show rather high pK a s (pK a = 18-21 in DMSO/H 2 O/Me 4 NOH). [13] Further, their utility in the generation of a multidentate ligand is severely limited by their complete rigidity.…”