The effects of cyclic terminal groups in 4-aminoazobenzene and related azo dyes. Part 3. Electronic absorption spectra of some monoazo dyes derived from N-phenylmorpholine, N-(phenyl)thiomorpholine, N-(phenyl)thiomorpholine 1,1-dioxide, and N-acetyl-N′-phenylpiperazine

Spectral Tuning of Azobenzene Photoswitches for Biological Applications

“…Received: October 14, 2008 Revised: November 20, 2008 Published online: January 15,2009 . Keywords: azo compounds · isomerization · peptides · photoswitches…”

“…The presence of a six-membered ring (5 c, 5 e, 5 f) introduces steric interactions that lead to loss of sp 2 character on the N atom, whereas a five-membered ring (5 d), or no ring at all (5 a, 5 b) produces enhanced N delocalization. [15,16] In addition, compounds 5 e and 5 f have heteroatoms in the 2,2' Scheme 1. Synthesis of 4,4'-diacetamido azobenzenes bearing amino substituents in the 2,2'-positions.…”

“…The presence of a six-membered ring (5 c, 5 e, 5 f) introduces steric interactions that lead to loss of sp 2 character on the N atom, whereas a five-membered ring (5 d), or no ring at all (5 a, 5 b) produces enhanced N delocalization. [15,16] In addition, compounds 5 e and 5 f have heteroatoms in the 2,2' substituents that are expected to decrease the basicity of the N atoms. [17] In general the expected relative electron-donating ability of the 2,2' substituents correlates with the wavelength of maximal absorption; species with the most electron donating pyrrolidino substituents (5 d) exhibit the longest wavelength absorption.…”

Azobenzene photoswitches for biomolecules

“…Substituents on the phenyl rings may strongly influence the position and shapes of azobenzene absorption bands. [25][26][27][28][29][30][31][32][33] For example, amino groups at the ortho or para positions can red-shift the spectrum dramatically. 11,34 Incorporating a donating group at one para position and an acceptor group at the other para position (such derivatives have been termed 'push-pull' azobenzenes) can lead to further red-shifts.…”

Fine‐tuned photochromic sulfonylureas for optical control of beta cell Ca2+ fluxes

“…3 Therefore, we decided to install different cyclic amines based on studies almost half a century ago showing their influence on 4-aminoazobenzene electronic absorption spectra. [15][16][17][18] The consequent "closed-ring" azobenzenesulfonylureas, spanning small-large cyclic structures, were subject to detailed chemical characterization before in vitro testing in pancreatic islets. While all the novel light-activated sulfonylureas showed photoswitching of beta cell Ca 2+ fluxes, those with a medium-sized pyrrolidine ring evoked the best ON-OFF responses.…”