Monitoring the photochemistry of a formazan over 15 orders of magnitude in time

Abstract

2,3,5-triphenyltetrazolium chloride (TTC) may convert into phenyl-benzo[c]tetrazolocinnolium chloride (PTC) and 1,3,5-triphenylformazan (TPF) under irradiation with light. The latter reaction, albeit enzymatically rather than photochemically, is used in so-called TTC assays indicating cellular respiration and cell growth. In this paper, we address the photochemistry of TPF with time-resolved spectroscopy on various time scales. TPF is stabilized by an intramolecular hydrogen bond and switches photochemically via an E-Z isomerization around an N=N double bond into another TPF-stereoisomer, from which further isomerizations around the C=N double bond of the phenylhydrazone group are possible. We investigate the underlying processes by time-resolved spectroscopy in dependence on excitation wavelength and solvent environment, resolving several intermediates over a temporal range spanning 15 orders of magnitude (hundreds of femtoseconds to hundreds of seconds) along the reaction path. In a quantum-chemical analysis, we identify 16 stable ground-state isomers and discuss which ones are identified in the experimental data. We derive a detailed scheme how these species are thermally and photochemically interconnected and conclude that proton transfer processes are involved.

Wavelength-dependent photochemistry of a salicylimine derivative studied with cryogenic and ultrafast spectroscopy approaches

“…It was already shown that ESIPT usually proceeds within less than or on the order of 100 fs, a general observation reported for many other substances in which ESIPT occurs. [60][61][62][63][64][65][66][67][68][69][70] Comparing to the calculations, the PES along the proton transfer coordinate (Fig. 3b) shows a barrierless character and a lowering of the S 1 state, which explains the rapid dynamics and the blue-shift that is observed.…”

Standardization of Quick Seed Viability Protocol for Pinus roxburghii Sarg. Using Tetrazolium Assay

“…The chir pine seeds were placed in the Petri dishes on the moistened double sheets of Watman filter paper No.1 to incubate with TZ solution at 25, 30 and 35 °C temperature in the darkness for 12, 24 and 36 hours. The 2,3,5-Triphenyl Tetrazolium Chloride (TTC) salt solution enters into the living tissue of the seed which produce a reddish or dark purple colour due to water insoluble compound called formazon by the activity of dehydrogenase enzyme [25]. After competition of incubation period, the TZ solution was drained out and chir pine seeds were washed in distilled water.…”