Revealing the effects of molecular orientations on the azo-coupling reaction of nitro compounds driven by surface plasmonic resonances

A recent report on the azo coupling of 4-nitrobenzo-15-crown-ether (4NB15C) and 4-nitrothiophenol (4NTP) indicated that the reaction barrier could be reduced greatly with surface plasmonic effects on silver dendritic nanostructures in aqueous solution. Accordingly, an azo coupling reaction mechanism...

Full description

Saved in:
Bibliographic Details
Published in:Physical chemistry chemical physics : PCCP 2021-10, Vol.23 (38), p.21748-21756
Main Authors: Shiu, Ying-Jen, Hayashi, Michitoshi, Lai, Ying-Huang, Jeng, U-Ser
Format: Article
Language:English
Subjects:
Aqueous solutions
Clusters
Configurations
Coupling (molecular)
Nanostructure
Nitro compounds
Plasmonics
Raman spectra
Reaction mechanisms
Surface plasmon resonance
Citations: Items that this one cites
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:A recent report on the azo coupling of 4-nitrobenzo-15-crown-ether (4NB15C) and 4-nitrothiophenol (4NTP) indicated that the reaction barrier could be reduced greatly with surface plasmonic effects on silver dendritic nanostructures in aqueous solution. Accordingly, an azo coupling reaction mechanism was proposed based on one or two SERS peaks. Toward a profound understanding of this azo coupling reaction mechanism, it is crucial to scrutinize the origin of the full SERS spectrum. Here, we construct a molecular model consisting of 4NTP and 4NB15C on an Ag 7 cluster that simulates a silver dendritic nanostructure, and investigate the SERS spectra of the azo coupling of these two molecules. We propose five different adsorption sites and 13 different orientations of 4NTP on the Ag 7 cluster and optimize the geometries of the five configurations. With each optimized configuration of 4NTP adsorbed on Ag 7 , we further consider the azo coupling product with a 4NB15C molecule and simulate the corresponding Raman spectra. Comparing the measured Raman spectra and model analysis, we conclude that the azo coupling reaction depends decisively on a parallel molecular orientation of the adsorbed 4NTP relative to the facets of Ag 7 , the orientation of which further directs the subsequent reaction for the product of 4NB15C-4NTP. Simulated SERS from the preferred molecular orientations of 4NTP and the azo product 4NB15C-4NTP at the bridge site and in parallel with the facets of an adsorbed silver cluster.
ISSN:1463-9076
1463-9084
DOI:10.1039/d1cp03041h