Nature of Linear Spectral Properties and Fast Electronic Relaxations in Green Fluorescent Pyrrolo[3,4-c]Pyridine Derivative

Abstract

The electronic nature of 4-hydroxy-1H-pyrrolo[3,4-c]pyridine-1,3,6(2H,5H)-trione (HPPT) was comprehensively investigated in liquid media at room temperature using steady-state and time-resolved femtosecond transient absorption spectroscopic techniques. The analysis of the linear photophysical and photochemical parameters of HPPT, including steady-state absorption, fluorescence and excitation anisotropy spectra, along with the lifetimes of fluorescence emission and photodecomposition quantum yields, revealed the nature of its large Stokes shift, specific changes in the permanent dipole moments under electronic excitation, weak dipole transitions with partially anisotropic character, and high photostability. Transient absorption spectra of HPPT were obtained with femtosecond resolution and no characteristic solvate relaxation processes in protic (methanol) solvent were revealed. Efficient light amplification (gain) was observed in the fluorescence spectral range of HPPT, but no super-luminescence and lasing phenomena were detected. The electronic structure of HPPT was also analyzed with quantum-chemical calculations using a DFT/B3LYP method and good agreement with experimental data was shown. The development and investigation of new pyrrolo[3,4-c]pyridine derivatives are important due to their promising fluorescent properties and potential for use in physiological applications.

Selecting molecular or surface centers in carbon dots-silica hybrids to tune the optical emission: A photo-physics study down to the atomistic level

“…Concerning the two molecules, the results on CZA agree with previously reported ones [40,74], calling for the assignment of the blue emission to this molecule when a blue molecular center is observed. Surprisingly, the results on HPPT do show an absorption transition at 330 nm, quite far away from the expected absorption at about 400 nm experimentally reported [20] and recently calculated but to a lower theory level (B3LYP and 6-31G(d,p) basis set [86]) for the anionic form of HPPT. A theoretical in-depth analysis of these results is beyond the scope of the present research and will be discussed in further work.…”

The role of molecular fluorophores in the photoluminescence of carbon dots derived from citric acid: current state-of-the-art and future perspectives

“…104 Interestingly, PL QY values determined for pure HPPT differ markedly from those reported for green-emitting fractions collected after the chromatographic separation of CDs (in which the presence of HPPT as the main component was confirmed via NMR experiments). Thus, the PL QY of pure HPPT in aqueous solutions was determined to be in the range of 0.09–0.15 (0.29 in MeOH), 40,107 while for the green-emitting fraction it was reported to be around 0.27 (0.70 in MeOH). 87 This increase in emissive behavior could be clarified by the possible non-covalent interactions of HPPT with other components of CDs or simply by its immobilization inside the CD decreasing the vibrational modes and thus the nonradiative relaxation rate.…”

Synthesis of Pyridin-1(2H)-ylacrylates and the Effects of Different Functional Groups on Their Fluorescence

“…Linking pyridines with other π-conjugated motifs can provide a simple and efficient means for preparing non-multi-ring-fused fluorescent materials [ 39 , 40 , 41 ]. While examples of such systems include imidazo-pyridines [ 42 , 43 ] and pyrrolo [3,4- c ]pyridines [ 44 ], as well as coumarin–pyridine [ 45 ] and pyridine–triazole–coumarin conjugates [ 46 ], only a few embody pyridine/open-π-chain constructs. Cyanopyridines [ 47 , 48 ] are perhaps the most conspicuous examples of these and are known to be excellent fluorescence agents with the photophysical properties of such conjugated systems able to be fine-tuned through the introduction of different substituents on the heterocyclic ring (and that are thought to, inter alia, affect crystal packing and the associated band gaps).…”