Vibrational Band Assignments for the Chiral Modifier Cinchonidine:  Implications for Surface Studies

Abstract

Vibrational assignments for the chiral molecule cinchonidine using a combination of experimental vibrational spectroscopic measurements and ab initio computational methods are reported. Several bands in both the IR and Raman spectra are identified as useful in providing information regarding the mode of adsorption of cinchonidine on metal surfaces, a system of great relevance to enantioselective catalysis. In particular, vibrational modes associated with the quinoline group can be used to diagnose the degree of tilt of the molecule with respect to the plane of the substrate. The use of this information for the study of cinchonidine adsorption on polycrystalline platinum with both reflection−absorption infrared spectroscopy (RAIRS) and surface-enhanced Raman spectroscopy (SERS) is discussed. Adsorption geometries for cinchonidine on platinum at low and high concentrations are reported.

Surface-Enhanced Raman Scattering: A Powerful Tool for Chemical Identification

“…Since its first discovery in the late 1970s, 6 SERS has thus been an object of great interest in many areas of science and technology, including chemical analysis, corrosion, lubrication, heterogeneous catalysis, biological sensors, and molecular electronics. [7][8][9][10][11] It has long been believed that two enhancement mechanisms, one called a long-range electromagnetic (EM) effect, and the other called a short-range chemical (CHEM) effect, are simultaneously operative for SERS. 1,3,12 Theoretically, at least 8 -10 orders of magnitude can arise from electromagnetic surface plasmon excitation, while the enhancement factor due to the chemical effect is 10 1 -10 2 times.…”

Comparative Characteristics of Gold-Gold and Gold-Silver Nanogaps Probed by Raman Scattering Spectroscopy of 1,4-Phenylenediisocyanide

“…[6][7][8][9][10] The phenomenon of SERS is thus practical and highly attractive, but surprisingly the origin of SERS has not yet been clearly clarified, although electromagnetic and chemical enhancement mechanisms are definitely responsible for the occurrence of SERS.…”

Effect of Interaction Energies on the Adsorption of Glycine onto a Cu(110) Surface: A Monte Carlo Simulation

“…One promising route for achieving this is to use chiral modifiers to endow enantioselective properties onto a metallic surface (Baiker and Blaser 1997). This modification of the surface may act selectively towards the adsorption of another chiral probe species in two ways: (a) through a oneto-one mechanism, either by the formation of a complex between an individual modifier molecule and the reactant or by the creation of a single selective site on one side of the modifier (Tungler et al 1989;Baiker 1997;LeBlond et al 1999;Bürgi and Baiker 2000;Kubota and Zaera 2001;Chu et al 2003;Ma and Zaera 2005) and (b) through a template mechanism, in which the chiral modifier adsorbs forming a superstructure, while the template which contains void spaces acts selectively on the adsorption of one of the enantiomers of the probe chiral species through symmetry effects (Raval 2001;Ortega Lorenzo et al 1999;Humblot et al 2004;Stacchiola et al 2002Stacchiola et al , 2005Romá et al 2004;Lee and Zaera 2005).…”

“…This steric effect is probably closely related to the superstructure chiral species formed on metal single crystals, which sometimes present an "extended chirality" (Raval 2002;Humblot and Raval 2005), and this, in turn, should depend strongly on the footprint of the adsorbed chiral species (i.e. the geometric form of the set of adsorbing sites occupied by the adsorbed species, or the projection of the adsorbed species on the metallic surface) and on the interactions between the adsorbed species (Humblot and Raval 2005; Barlow et al 2004Barlow et al , 2005.…”