Molecular spectroscopic probes

There has recently been much activity in developing molecular spectroscopic probes of electrochemical interfaces, as for other types of heterogeneous systems. The ultimate objectives of these efforts include not only the characterization of adsorbate molecular structure interactions under equilibrium conditions, but also the extraction of mechanistic and kinetic information from spectral detection of reactive adsorbates. 

Grieser F, Dummond CJ (1988) The physicochemical properties of self-assembled surfactant aggregates as determined by some molecular spectroscopic probe techniques. J Phys Chem 92 5580-5593... 

Up to this poinL we have primarily focused our attention on the application of theo-oprical characterization techniques for monitoring the dynamics of supramolecular stmctures, such as the spatial reorganization of crystals and microphase-separated domains, in various polymeric systems under the influence of flow, deformation, and relaxation. We now shift our attention to rheo-oprical analysis at submolecular scale by using molecular spectroscopic probes. In particular, a rheo-oprical technique called dynamic infrared linear dichroism (DIRLD) spectroscopy, capable of monitoring segmental dynamits of polymer chains, is described. 

Luminescence spectroscopy provides simple access to the splitting of the ground multiplet but this technique is not always accessible due to nonradiative decay and strong ligand absorptions as encountered, for example, in the [Ln(Pc)]-/0 systems. For these reasons, alternative spectroscopic tools should be available for magnetochemists. The use of INS as a spectroscopic probe for molecular magnetic systems has recently been reviewed by Guidi [36], Amoretti et al. [37]... 

NMR is the most fundamental molecular specific probe of diffusion. Polymer motions and the spectroscopic signature of a given nucleus can be unambiguously related to a particular morphological domain. The size and time scale of the experiments are such that the fundamental hopping events of diffusing molecules can be sampled. 

Molecular spectroscopy is a key method in almost all fields of ILs research. Starting with the assessment of the purity of ILs and study of their properties using different spectroscopic probes and their absorption and emission spectra, the reactions taking place in ILs are almost impossible to be studied without using molecular spectroscopy. Recording the UV-Vis or luminescence spectra is a commonly used technique for the detection of compounds by chromatography and electrophoresis, and ILs are more widely used in the respective studies. So, it is important to further investigate the applicability of ILs to molecular spectroscopy. 

Structural information regarding the molecular orientation of adsorbates on electrodes can be obtained using a number of Raman spectroscopic probes. While these experiments are not routine to conduct, they are beginning to approach the simplicity of the FTIRRAS experiments just described. Figure 9.13... 

M. Suhm (ed.), Spectroscopic probes of molecular recognition. Phys. Chem. Chem. Phys. 9 (32), 4443 (2007)... 

Lees AJ (2001) Luminescent metal complexes as spectroscopic probes of monomer/polymer environments. In Ramamurthy V, Schanze KS (Eds) Optical Sensors and Switches. Molecular and Supramolecular Photochemistry Series, Vol 7, Chap 5. Marcel Dekker, New York, p 209... 

The advent of supersonic molecular beam expansion techniques and high spectral-and time-resolved laser spectroscopic probing has transformed experimental... 

UV-visible, fluorescence, and IR spectroscopy have been used to characterize the solvent strength of pure and mixed supercritical fluid solvents, and to study solute-solvent interactions. The use of spectroscopic probes for the determination of clustering of pure and binary supercritical fluids about solutes is discussed. Spectroscopic studies of solvent strength and solute-solvent interactions are valuable for the development of molecular thermodynamic theory, engineering models, and for the molecular design of separation and reaction processes. 

Also, various spectroscopic quantities can be calculated in order to test experimental assumptions Once a structure of a supramolecular assembly has been assumed, optimized or propagated in time, properties like vibrational frequencies, infrared, Raman [93], or Resonance Raman [159] intensities, NMR or EPR parameters can be calculated with first-principles methods to be compared with the experimentally measured spectra in order to confirm or reject the structural basis assumed in the interpretation of the experimental spectra. It is impossible to review the work and achievements of theoretical chemistry in this respect. Therefore, we concentrate on selected examples in the following. The interested reader is referred to the book by Kaupp, Biihl and Malkin [160] for the calculation of NMR and ESR parameters and to Refs. [161, 162] for more general discussions of molecular property calculations. NMR parameters are molecular properties probed at atomic nuclei and thus ideal for linear-scaling or empirical approaches. An efficient linear-scaling method for supramolecular systems has been presented recently [163]. 

A molecular description of detonation, particularly initiation, has been pursued for decades, with little success. One difficulty has been obtaining high-quality data at the appropriate length and time scales and with molecular specificity. What are the appropriate time and space scales Detonation waves have tjqjical velocities of 6-8 km/s, or equivalently 6-8 nm/ps. Recent molecular dynamics studies suggest that reactions in shocked energetic materials can occur in times as short as a few ps [1-6]. Energy transfer studies on molecular systems also reveal similar fast time scales [7-11]. Therefore, appropriate spectroscopic probes should have ps or better time resolution. Also, shock rise time measurements with sub-ps resolution require samples with surface uniformity better than 6-8 nm over the probed area. 

---