In situ Raman monitoring of [2+2] cycloaddition of pyridine substituted olefins induced by visible laser

Abstract

Visible laser induced [2+2] cycloaddition of solid-state pyridine substituted olefins into cyclobutane has been monitored by an in situ Raman technique. The laser power and wavelength can dramatically alter the reaction kinetics, as a prior melting process (heating from laser irradiation) is required for this [2+2] photoreaction.

In Situ Raman Monitoring of Silver(I)‐Aided Laser‐Driven Cleavage Reaction of Cyclobutane

“…[25] Silver (I) trifluoroacetate (AgTFA) was purchased from Sigma-Aldrich. [25] Silver (I) trifluoroacetate (AgTFA) was purchased from Sigma-Aldrich.…”

“…[12,13] Besidesc onventional heat resources, laser irradiation can also be applied to induce cleavage reaction. [22][23][24] In our previousw ork, [25] we managed to monitor the dimerization reaction process of pyridyl-substituted olefinsi nto cyclobutanes through the in situ Ramans pectra,w here the laser is the heat source and silver(I)i onsa ct as at emplate to control the pyridyl-substituted paralleled olefins' distance to within 4.2 . [9,16] In situ time-resolved Raman spectroscopy is an advancedt echnique that can monitor the reaction processes and structure changes of molecules.…”

“…[17][18][19] Moreover,R aman spectroscopyi su ltrasensitive to bond vibration, [19][20][21] as opposed to in situ X-ray diffraction, which is only sensitivet oc rystalline structure, so Ramans pectroscopy can even be applied to amorphousm aterials during the reactionp rocess. [25] For the [Ag 3 (DCCB)][TFA] 3 crystal,besides the Raman fingerprints of DCCB, one new band at approximately 943 cm À1 can be found, corresponding to the bisacetato CÀCs ymmetric vibration of C=O-Ag-O = C. [26,27] Importantly,u pon 633 nm laser (100 %p ower,3mW) irradiation, Figure 1. However,t he newly formed cyclobutane would not undergo cleavage in ambient conditions, owing to its chemically stable conformation.…”

“…[14,15] Typically,e xsitu techniques such as nuclear magnetic resonance (NMR) spectroscopy and mass spectrometrya re used to study the yield of the cyclobutane cleavage reactions, which fail to monitor the whole reaction process. [22][23][24] In our previousw ork, [25] we managed to monitor the dimerization reaction process of pyridyl-substituted olefinsi nto cyclobutanes through the in situ Ramans pectra,w here the laser is the heat source and silver(I)i onsa ct as at emplate to control the pyridyl-substituted paralleled olefins' distance to within 4.2 . [17][18][19] Moreover,R aman spectroscopyi su ltrasensitive to bond vibration, [19][20][21] as opposed to in situ X-ray diffraction, which is only sensitivet oc rystalline structure, so Ramans pectroscopy can even be applied to amorphousm aterials during the reactionp rocess.…”

“…As shown in Figure 2b,t he Ramans pectrumo fD CCB is dominated by the pyridine ring stretching at approximately 1610 cm À1 ,p yridine ring breathing at 1020 cm À1 ,t he cyclobutane skeletal CÀCs tretching mode and C(cyclobutane)-C(pyridine) at 1145 and 845 cm À1 ,r espectively,a sw ella sC H 2 deformation at 1430 and 1370 cm À1 . [25] For the [Ag 3 (DCCB)][TFA] 3 crystal,besides the Raman fingerprints of DCCB, one new band at approximately 943 cm À1 can be found, corresponding to the bisacetato CÀCs ymmetric vibration of C=O-Ag-O = C. [26,27] Importantly,u pon 633 nm laser (100 %p ower,3mW) irradiation, Figure 1. Crystals tructure of [Ag 3 (DCCB)][TFA] 3 (CCDCN o.…”