Metalation of 5,10,15,20-tetrakis(1-methyl-4-pyridyl)porphyrin in silver colloids studied via time dependence of surface-enhanced resonance Raman spectra

Abstract

In SERS-active systems, when a free base porphyrin is adsorbed at a roughened metal surface, the metal ion may be incorporated into the porphyrin core. We have investigated the metalation kinetics of 5,10,15,20-tetrakis(1methyl-4-pyridyl)porphyrin (TMPyP), reÑected in the time evolution of its SERRS spectra. To establish proper metalation Raman markers, resonance Raman spectra of the free base and chemically Ag metalated TMPyP forms were measured under di †erent conditions. The increase in intensity of the 395 cm-1 line, the decrease in intensity of the 329 cm-1 line, the reduction of the 1337 + 1360 cm-1 doublet to one strong line at 1340 cm-1 and the vanishing of the 1140 cm-1 medium line (the last exceptionally for 514.5 nm excitation) were found to be suitable markers for quantitative analysis. All other spectral changes related to metalation may coincide with e †ects caused by other variations of the porphyrin state. Time evolution of the porphyrin metalation was studied in various Ag colloid systems, with or without phosphate anions, citrate and/or Triton X-100. Time-dependent SERRS spectra of TMPyP were recorded within periods from minutes to several hours. Factor analysis of the SERRS spectra proved that the spectral changes were induced by only one phenomenon (metalation). The SERRS spectra were decomposed into the spectrum of the free base TMPyP and that of its Ag metalated form, and the metalation kinetics were determined by means of the time dependence of the metalated form portion in the SERRS spectrum. The results show a remarkable reliance on the state of the metal surface.

Surface chemistry of porphyrins and phthalocyanines

“…On mixed Ag-Cu colloids with up to 5 at % Cu, all adsorbates were converted to Cu(II)TMPyP 4 þ [727]. The metalation kinetics of 2HTMPyP 4 þ on Ag colloids was investigated by time-dependent SERRS and was found to be highly dependent on the presence of anions in the system [728,729]. In another study, Zn(II) ions adsorbed on silica gel reacted rapidly with solutions of 2HTPP to ZnTPP.…”

Colloidal systems of silver nanoparticles and high-regioregular cationic polythiophene with ionic-liquid-like pendant groups: Optical properties and SERS

“…The spectra were accumulated for 150 s for each measurement. A baseline correction, normalization (the 681 cm À1 DMSO band was used as an internal intensity standard for the amplification factor determination) and quantitative analysis of Raman spectra were carried out using factor analysis (FA) [25]. FA provides a set of orthonormal subspectra S j , weights W j , and scores V ij representing the relative proportion of the…”

Interaction of phospholipid dispersions with water-soluble porphyrins as monitored by their Raman temperature profiles

“…The factor dimension can be derived from the dependence of the residual error on the increased number of terms at the right side of Eq. (1) (Hanzlíková et al, 1998).…”

“…In further analysis, pure spectral forms P GEL and P LC representing spectra of the phospholipid dispersion in the gel and liquid crystal phase, respectively, were constructed as proper linear combinations of the first and second subspectra analogously to the procedure used by Hanzlíková et al (1998). The main criterion to estimate the correct value of the multiplier in the combination is the best similarity of constructed spectra with the first and last spectra in the experimental series without any sign of a spectral subtraction of the other form.…”