1352391-67-3Relevant academic research and scientific papers
Influence of the cavity size of cyclodextrins on the photochromism of azoimidazoles
Gayen, Pallab,Karmakar, Abhisake,Sepay, Nayim,Sinha, Chittaranjan
, (2021/12/20)
1-Alkyl-2-(arylazo)imidazole (RaaiR/) exists in trans configuration about the –N[dbnd]N- bond. Upon optical excitation in UV region the trans-configuration isomerises to cis-RaaiR/. The photochromism is very susceptible to internal substituents and external environment like solvent polarity, viscosity and presence of innocent foreign species. In this work, the trans-to-cis photoisomerisation of RaaiR/has been studied in DMF solution of cyclodextrin (α/β/γ-CD). The rate of trans-to-cis isomerisation is decreased in presence of CD compared to native form of RaaiR/. The quantum yield of the photoisomerisation is decreased by 35–55% in inclusion phase, CD@RaaiR/, than free photochrome and follows the rate sequence: free state > γ-cyclodextrin > β-cyclodextrin > α-cyclodextrin. The cis-to-trans isomerisation proceeds slowly in visible light irradiation while it is appreciably fast with increasing temperature. The activation energy (Ea) of cis → trans thermal isomerisation is also diminished compared to free state of photochrome. The absorption spectral studies have been used in case of Pai-C18H37 with β-CD and inclusion constant is Kb ?= ?0. 121 M?1. The 1H NMR spectral measurement also suggests interaction of aryl protons with cavity protons of β-CD. DFT computation is also attempted to examine the inclusion of RaaiR/with CD and the negative values of binding energy show that the process of inclusion is spontaneous and complexes formed are stable.
The synthesis, structure and photochromism of mercury(II)-iodide complexes of 1-CnH2n+1-2-(arylazo)imidazoles (n = 4, 6, 8)
Mallick, Debashis,Nandi, Avijit,Datta, Shilpi,Sarker, Kamal Krishna,Mondal, Tapan Kumar,Sinha, Chittaranjan
experimental part, p. 506 - 514 (2012/03/12)
The reaction of HgI2 with 1-CnH2 n+1-2-(arylazo)imidazole (Raai-CnH 2n+1 where n = 4, 6, 8) has isolated iodide bridging dimeric complexes, [Hg(RaaiCnH2n +1)(μ-I)(I)]2. The structures of the ligand and the complexes have been established by spectral (UV-Vis, IR, 1H NMR) data. One of these complexes [Hg(1-hexyl-2-(p-tolylazo)imidazole)(μ-I)(I)] 2 has been structurally confirmed by single crystal X-ray diffraction study. The ligand, Raai-CnH2n+1 exists at ambient condition in trans geometry about azo (-NN-) group; the UV light irradiation in MeOH solution shows E-to-Z isomerisation. The reverse transformation, Z-to-E, is very slow with visible light irradiation while isomerises rapidly on heating. The coordinated ligand, Raai-CnH 2n+1 in the complexes exhibit similar behaviour in DMF solution. Quantum yields (φE→ Z) of E-to-Z isomerisation are higher for free ligands than that of their metal complexes. The Z-to-E isomerisation is a thermally induced process. The activation energy (Ea) is calculated by controlled temperature experiment.
