Porphyrin based hybrid borate glasses: Structure and photophysical investigation

Freebase tetra phenyl porphyrin (H2TPP) and its derivatives in different concentration ranges (0.5–2.0 mg per 12 g of boric acid) were incorporated into borate glass matrix by melt quenching technique at 230 °C. The formed glasses were stable and in green colour. The optical absorption and emission properties are different from that observed in solutions. The absorption spectrum shows a two line pattern Soret band at 435–454 nm and Q-band at 665–701 nm. The emission spectrum shows strong S2 → S0 emission at 490–520 nm region and S1 → S0 emission at 725–810 nm. The time resolved fluorescence decay of S1 → S0 emission shows three exponential decay. For example, in the case of 2 mg of H2THP doped glass the lifetimes were found to be τ1 = 0.511 ns (26.7%), τ2 = 10 ps (64.68%) and τ3 = 3.965 ns (8.62%). These unusual photophysical properties were found to arise from different structural motifs of porphyrin in the glass. These structures were further modeled through reactions of porphyrin with BF3O(C2H5) in solution and DFT calculations.