Spectroscopy and Tautomerization Studies of Porphycenes

Abstract

Tautomerization in porphycenes, constitutional isomers of porphyrins, is strongly entangled with spectral and photophysical parameters. The intramolecular double hydrogen transfer occurring in the ground and electronically excited states leads to uncommon spectroscopic characteristics, such as depolarized emission, viscosity-dependent radiationless depopulation, and vibrational-mode-specific tunneling splittings. This review starts with documentation of the electronic spectra of porphycenes: Absorption and magnetic circular dichroism are discussed, together with their analysis based on the perimeter model. Next, photophysical characteristics are presented, setting the stage for the final part, which discusses the developments in research on tautomerism. Porphycenes have been studied in different experimental regimes: molecules in condensed phases, isolated in supersonic jets and helium nanodroplets, and, recently also on the level of single molecules investigated by optical and scanning probe microscopies. Because of the rich and detailed information obtained from these diverse investigations, porphycenes emerge as very good models for studying the complex, multidimensional phenomena involved in the process of intramolecular double hydrogen transfer.

Exploring the Effect of Gold Support on the Oxygen Reduction Reaction Activity of Metal Porphycenes

“…Herein, we use density functional theory to systematically study the effect of the gold support on the ORR activity of the first row 3d transition metal‐porphycenes (MPc). Porphycene (Pc) is a constitutional isomer of porphyrin exhibiting interesting magnetic, optical, electrical and mechanical properties similar to porphyrin . Metal‐porphycenes supported on metal surfaces have attracted much attention in recent years owing to their potential application in designing molecular switches, sensors or photovoltaic devices .…”

“…[38,39] similar to porphyrin. [40][41][42] Metal-porphycenes supported on metal surfaces have attracted much attention in recent years owing to their potential application in designing molecular switches, sensors or photovoltaic devices. [43][44][45] Here, we focus on the ORR activity of unsupported molecular and gold supported 3d MPc (Figure 1).…”

Trendbericht Physikalische Chemie 2017: Atomare und molekulare Tunnelprozesse

“…136) Dazu kamen Untersuchungen an Einzelmolekülen mit einem Rastertunnelmikroskop (Scanning Tunneling Microscope, STM). 137,138) Die eindimensionale Rotationsbewegung des CH 2 Cl-Radikals um die C-Cl-Achse wurde mit IR-Spektroskopie untersucht, nachdem CH 2 ClI bei 3,7 K in Parawasserstoff zu CH 2 Cl • photodissoziiert wurde. Dabei wandelte sich die Kernspinsymmetrie zwischen ortho und para innerhalb einiger Stunden um.…”

Acid- and hydrogen-bonding-induced switching between 22-π and 18-π electron conjugations in 2-aminothiazolo[4,5-c]porphycenes

“…1 Their isolation and structural characterisation open up new avenues for the research in multiple fields such as photodynamic therapy, [2][3][4][5] organic solar cells, 6-8 catalysis 9,10 and theranostics. 11 Over the last decade, the photophysical properties of symmetric and asymmetric 18-p porphycene derivatives have been studied, revealing specific properties such as the N-H tautomerization 12,13 or nonlinear optical properties [14][15][16] which set them apart from other related 18-p porphyrinoids. Of particular interest is the N-H tautomerization process in 9-substituted asymmetric porphycene derivatives as high electron-donating substituents in the 9-position leads to an enhanced energetic-splitting between the two transtautomers resulting in dual fluorescence emission.…”