Structure and Spectroscopy

W /(a) Calculate the frequencies of violet and red light if their wavelengths are 400 and 750 nm, fhvCalculate and compare the energies of their photons. -4 

Photons of violet light have more energy than those of red light. 

In a typical spectrophotometer, a dissolved compound is exposed to electromagnetic radiation with a continuous spread in wavelength. The radiation passing through or absorbed is recorded on a chart against the wavelength or wave number. Absorption peaks are plotted as minima in infrared, and usually as maxima in ultraviolet spectroscopy. 

At a given wavelength, absorption follows an exponential law of the form 

The wavelength of maximum absorption, /.max, and the corresponding max are identifying properties of a compound. Units are normally omitted from specifications of e. 

Spectral properties are used to determine the structure of molecules and ions. Of special importance are ultraviolet (uv), infrared (ir), nuclear magnetic resonance (nmr), and mass spectra (ms). Free radicals are studied by electron spin resonance (esr). 

Wavelengths (A) for ultraviolet spectra are expressed in nanometers (lnm= 10 m) for the infrared, micrometers are used (1 /im = 10 m). Frequencies (i ) in the infrared are often specified by the wave number i , where p = 1/A a common unit for P is the reciprocal centimeter (1 cm = 100m ). The basic SI units for frequency and energy are the hertz (Hz) and the joule (J), respectively. 

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The phosphinimide phosphanes 42 [75b], which are similar to the acyclic diphosphazanes comprising of one nitrogen and phosphorus atom, when treated with AlMea, (Scheme 19), were found to coordinate to the P(III) center to yield the alane adducts 43 which were characterized by the P-NMR spectroscopy and structure elucidation of 43a. 

Lutz HD (1995) Hydroxide Ions in Condensed Materials - Correlation of Spectroscopy and Structural Data. 82 85-104... 

Solomon, E. I., and Lever, A. B. P., Eds. (2006). Inorganic Electronic Spectroscopy and Structure, Vols. I and II. Wiley New York. Perhaps the ultimate resource on spectroscopy of coordination compounds. Two volumes total 1424 pages on the subject. 

J. M. Lisy, Spectroscopy and structure of solvates alkali metal ions. Int. Rev. Phys. Chem. 16, 267 289 (1997). 

J. Yarwood, Spectroscopy and Structure of Molecular Complexes, Plenum Press, London, 1973, p. 217. 

Case study on Raman spectroscopy and structure of imidazolium-based ionic liquids... 

Visible Absorption Spectroscopy and Structure of Cyanine Dimers in Aqueous Solution 176... 

K. Nakamoto, P. J. McCarthy. Spectroscopy and Structure of Metall Chelate Compounds. New York—London—Sydney, Intersciense Press, 1968. 

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