Substituent and solvent effects on the N‐2—N‐3 hindered rotation of cis‐1,3‐diphenyltriazenes

Abstract

Laser‐flash photolysis techniques were applied to investigate the dependence of the rotational barrier about the N‐2—N‐3 bond of symmetrically 4,4′‐disubstituted cis‐1,3‐diphenyltriazenes on substituents and solvents. The increase in the rotational barrier with increasing ability of the 4‐substituent to withdraw electrons implies the intramolecular process to be more susceptible to the electronic character of the aryl group attached to N‐1 than of that bonded to N‐3. Furthermore, the increase in the rotational barrier with decreasing solvent polarity implies an increase in dipole moment on rotation from the ground state to the transition state. Copyright © 2004 John Wiley & Sons, Ltd.

A series of 1‐[2‐aryl‐1‐diazenyl]‐3‐({3‐[2‐aryl‐1‐diazenyl]perhydrobenzo[d]imidazol‐1‐yl}methyl)perhydrobenzo[d]imidazoles. Synthesis and characterization

“…1,8,10,17-Tetraazapentacyclo[8.8.1.1 8,17 .0 2,7 .0 11,16 ]icosane (7) (1.38 g) was dissolved in 15 mL of 37% formaldehyde with gentle heating and stirring. The resulting solution was cooled to 0 ºC with an ice-salt bath and left to stir for thirty minutes.…”

“…Chemical shifts were recorded in CDCl 3 solutions at 20 ºC, and are relative to TMS internal standard. Elemental analysis was carried out by the Canadian Microanalytical Laboratory, Delta, B.C., Canada 1,8,10,17-Tetraazapentacyclo[8.8.1.1 8,17 .0 2,7 .0 11,16 ]icosane (7).…”

“…A variety of recrystallisation methods were used with various solvents in attempts to purify the crude solids. Physical data for the products are shown in Table 1 8,17 .0 2,7 .0 11,16 ]icosane (7) (1.71 g) was dissolved in 15 mL 37% formaldehyde with gentle heating and the solution was cooled to 0 ºC using an ice-salt bath while stirring for thirty minutes. The resulting solution was then slowly added to the diazonium salt solution (0.008 mol) dropwise, keeping the temperature between 0 ºC and 5 ºC, and then left to stir for thirty minutes at 0 ºC before being basified to pH 8 using a saturated NaHCO 3 solution.…”

Synthesis and Characterization of a Series of 1-Aryl-4-[aryldiazenyl]- piperazines. Part I. Isomers of N-(2,3-Dimethylphenyl)-N’-(Aryldiazenyl)- Piperazines

“…However, some of the triplet peaks were not resolved resulting in broad peaks, especially for H a . Such observation was due to the restricted rotation of the nitrogen-nitrogen single bond in the triazene subunit [6]. …”

Síntese e propriedades espectroscópicas e eletroquímicas de uma triazeno-porfirina

“…Na Figura 27 são mostrados os espectros de absorção da triazeno-porfirina H 2 MTTPP, em solução de (a) DCM e (b) MeOH, contendo os espectros de absorção da porfirina na forma neutra (preto) e na forma do ânion H 2 MTTPP ânion (vermelho), respectivamente. Os valores dos pKa´s do anel das porfirinas foram determinados, considerando-se um equilíbrio envolvendo dois prótons 165 , no caso da porfirina, e um próton da unidade diazoamínica 166,167 , como mostrado nas Equações I a IV, sendo a equação IV somente válida para equilíbrios ácido-base que envolvem dois prótons simultâneos (2H + ).…”