Structure and Spectra

All spectroscopic methods indicate that benzodiazepines exist in the dianil form 1 rather than in the isomeric conjugated forms 2 or 3. However, it has been noted4 that when a solution of the purple 2,4-dimethylbenzo-diazepinium hydrochloride was basified, a yellow solution resulted which, after a few seconds, turned colorless. This was attributed to initial formation of the conjugated base (2) which rapidly tautomerized to the normal dianil form.4 

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Pariser R 1956 Theory of the electronic spectra and structure of the polyacenes and of alternant hydrocarbons J. Chem. Rhys. 24 250-68... 

Herzberg G 1971 The Spectra and Structures of Simple Free Radicals An Introduction to Molecular Spectroscopy (Ithaca, NY Cornell University Press)... 

Herzberg G 1961 The spectra and structures of free methyl and free methylene Proc. R. Soc. A 262 291-317... 

A series of monographs and correlation tables exist for the interpretation of vibrational spectra [52-55]. However, the relationship of frequency characteristics and structural features is rather complicated and the number of known correlations between IR spectra and structures is very large. In many cases, it is almost impossible to analyze a molecular structure without the aid of computational techniques. Existing approaches are mainly based on the interpretation of vibrational spectra by mathematical models, rule sets, and decision trees or fuzzy logic approaches. 

This vibrational cooling is sufficient to stabilize complexes that are weakly bound by van der Waals or hydrogen-bonding forces. The pure rotational spectra and structure of species such as... 

Comparison of four pairs of compounds where the structures of both rhodium and iridium analogues are known shows dangers of drawing correlations between spectra and structure, even with isoelectronic compounds. 

Mass Spectra and Chemical Structure While there are a number of books (Refs 16, 30, 49 64) already referred to, which deal with details of the instrumentation and techniques of mass spectrometry, there are several concise introductory texts (Refs 10, 21 52) on the interpretation of mass spectra. Still other recent books deal comprehensively with organic structural investigation by mass spectrometry. One of these (Ref 63) discusses fundamentals of ion fragmentation mechanisms, while the others (Refs 7, 15, 20, 28 29) describe mass spectra of various classes of organic compounds. In the alloted space for this article methods of interpretation of mass spectra and structural identification can not be described in depth. An attempt is, therefore, made only to briefly outline the procedures used in this interpretation... 

Electronic spectra and structural properties of complex tetracyanides of Pt, Pd and Ni, M. L. Moreau-Colin, Struct. Bonding (Berlin), 1972,10,167-190 (33). 

Absorption spectra and structure of lanthanide coordination compounds in solution. K. B. Yatsi-mirskii and N. K. Davidenko, Coord. Chem. Rev., 1979, 27, 223-273 (255). 

The spectra and structure of transition metal complexes with tetradentate macrocyclic ligands. K. B. Yatsimirskii and Y. D. Lampeka, Russ. Chem. Rev. (Engl. Transl), 1980, 49,1003-1020 (191). 

G. Herzberg, The Spectra and Structure of Simple Free Radicals, Cornell University Press, New York, 1971, p. 173. 

Moreau-Colin ML (1972) Electronic Spectra and Structural Properties of Complex Tetracyanides of Platinum, Palladium and Nickel. 10 167-190 Morf WE, see Simon W (1973) 16 113-160... 

Table 1 Matrix IR spectra and structural data of the perhalogenated carbenes and radicals formed in pyrolysis reactions.

Fraser, N., N. N. Greenwood, and P. Straughan Aluminium Hydride Adducts of Trimethylamine Vibrational Spectra and Structure. J. Chem. Soc. [London] 1963, 3742. 

Odutola, J. A., and T. R. Dyke. 1980. Partially deuterated water dimers Microwave spectra and structure. J. Chem. Phys. 72, 5062. 

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