Arylazoimidazole complexes of lead(II)-halide and their photochromism
IR@NISCAIR: CSIR-NISCAIR, New Delhi - ONLINE PERIODICALS REPOSITORY (NOPR)
View Archive Info| Field | Value | |
| Title |
Arylazoimidazole complexes of lead(II)-halide and their photochromism
|
|
| Creator |
Mallick, Debashis
Chowdhury, Bharati Sen, Chandana Sarkar, Kamal Krishna Jana, Srikanta Mondal, Sudipa Sinha, Chittaranjan |
|
| Subject |
Photochromism
Density functional calculations Arylazoimidazoles Lead halide complexes |
|
| Description |
418-426
Lead(II) complexes of 1-alkyl-2-(arylazo)imidazole (Raai-C<sub>n</sub>H<sub>2n+1</sub>), [Pb(Raai-C<sub>n</sub>H<sub>2n+1</sub>)X<sub>2</sub>] (X = Cl, Br, I; and Raai-C<sub>n</sub>H<sub>2n+1</sub>, R = H, Me and <em>n</em> = 4, 6, 8) have been characterized by UV-vis, IR and <sup>1</sup>H-NMR spectroscopy. The coordinated Raai-C<sub>n</sub>H<sub>2n+1</sub> in the complexes undergoes E-to-Z (<em>trans</em>-to-<em>cis</em>) isomerisation about the –N=N– group upon being irradiated with UV light in DMF solution. The rate and quantum yields of E-to-Z photoisomerisation (φ<sub>E→Z</sub>) of the complexes are poorer than the respective free ligand response and are also affected by the nature of halide present (Cl<sup>-</sup>, Br<sup>-</sup> and I<sup>-</sup>). Variation in physicochemical parameters may be correlated with the effective mass of the photochrome. The rate of isomerisation follows the sequence: [Pb(Raai-C<sub>n</sub>H<sub>2n+1</sub>)Cl<sub>2</sub>] < [Pb(Raai-C<sub>n</sub>H<sub>2n+1</sub>)Br<sub>2</sub>] < [Pb(Raai-C<sub>n</sub>H<sub>2n+1</sub>)I<sub>2</sub>]. The Z-to-E isomerisation has been carried out at varying temperatures (298–308 K) to determine the activation energy of Z-to-E (<em>cis</em>-to-<em>trans</em>) isomerisation (<em>E</em><sub>a</sub>: 47.09–63.42 kJ mol<sup>-1</sup>) and the entropy of activation (<img src='/image/spc_char/delta.gif' border=0>S<img src='http://www.niscair.res.in/jinfo/equation40.gif' border=0> : 166.52 to –109.0 J mol<sup>-1</sup> K<sup>-1</sup>) which is a large negative in the complexes. Theoretical calculation supports cleavage of Pb(II)-N(azo) bond followed by the –N=N– rotation in a three-coordinated symmetry rather than the four-coordinated symmetry. |
|
| Date |
2018-03-22T06:54:57Z
2018-03-22T06:54:57Z 2018-03 |
|
| Type |
Article
|
|
| Identifier |
0975-0975(Online); 0376-4710(Print)
http://nopr.niscair.res.in/handle/123456789/43985 |
|
| Language |
en_US
|
|
| Rights |
<img src='http://nopr.niscair.res.in/image/cc-license-sml.png'> <a href='http://creativecommons.org/licenses/by-nc-nd/2.5/in' target='_blank'>CC Attribution-Noncommercial-No Derivative Works 2.5 India</a>
|
|
| Publisher |
NISCAIR-CSIR, India
|
|
| Source |
IJC-A Vol.57A(03) [March 2018]
|
|