Abstract
A mechanism is proposed for the formation of stable dimers of 4′-nitro-4-dimethylaminoazobenzene dye (4′-nitro-DAB)2 in solution, the existence of which in a vapor phase was established in 1965. It is shown that (4′-nitro-DAB)2 dimers are stable also in neutral and moderately acidic solutions. Their UV–Vis spectra are similar to the spectra of the same solutions of 4-dimethylaminoazobenzene (DAB) containing DAB2 dimers as the ground state. Like DAB2, (4′-nitro-DAB)2 dimers are reversibly converted to di- and triprotonated dimers under conditions of low and moderate acidity. In the process, the yellow color of the initial solution changes to red. It is concluded that the great stability of the dimers in the liquid and vapor phases is due to their inter-monomer bonds being formed with the participation of electrons promoted from the sp2- orbitals of N-atoms in azo-groups N=N to the Rydberg 3s-orbitals of the N=N-group (Rydberg bonds). It is established that at high acidities, the triprotonated dimers (the red solution) decompose reversibly into diprotonated monomers (the yellow solution). Structural formulas are proposed for the protonated species.
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References
A. Hantzsch and F. Hilscher, Ber. Dtsch. Chem. Ges. 41, 1171 (1908).
W. M. Dehn and L. McBride, J. Am. Chem. Soc. 39, 1348 (1917).
A. Hantzsch, Ber. Dtsch. Chem. Ges. 52, 509 (1919).
A. Hantzsch and A. Burawoy, Ber. Dtsch. Chem. Ges. 63, 1760 (1930).
G. M. Badger, R. G. Buttery, and G. E. Lewis, J. Chem. Soc., 1888 (1954).
G. Cilento, E. C. Miller, and J. A. Miller, J. Am. Chem. Soc. 78, 1718 (1956).
E. Sawicki, J. Org. Chem. 21, 605 (1956).
E. Sawicki, J. Org. Chem. 22, 621 (1957).
I. Ya. Bershtein and O. F. Ginzburg, Russ. Chem. Rev. 41, 97 (1972).
P. F. Gordon and P. Gregory, Organic Chemistry in Colour (Springer, Berlin, 1983).
Yu. A. Mikheev, L. N. Guseva, and Yu. A. Ershov, Russ. J. Phys. Chem. A 91, 715 (2017).
Yu. A. Mikheev, L. N. Guseva, and Yu. A. Ershov, Russ. J. Phys. Chem. A 91, 1896 (2017).
Yu. A. Mikheev, L. N. Guseva, and Yu. A. Ershov, Russ. J. Phys. Chem. A 82, 1580 (2008).
Yu. A. Mikheev, L. N. Guseva, and Yu. A. Ershov, Russ. J. Phys. Chem. A 83, 792 (2009).
Yu. A. Mikheev, L. N. Guseva, and Yu. A. Ershov, Russ. J. Phys. Chem. A 84, 1778 (2010).
A. Streitwieser, Jr., Molecular Orbital Theory for Organic Chemists (Wiley, New York, 1961; Mir, Moscow, 1965).
H. S. Green, F. Jones, M. Syz, and Hch. Zollinger, Helv. Chim. Acta 48 (45), 389 (1965).
S. E. Sheppard and P. T. Newsom, J. Am. Chem. Soc. 64, 2937 (1942).
Yu. A. Mikheev, L. N. Guseva, and Yu. A. Ershov, Russ. J. Phys. Chem. A 89, 2036 (2015).
K. Yoshihiro, L. Hohl, and K. Akio, J. Phys. Chem. 84, 3417 (1980).
K. Higasi, H. Baba, and A. Rembaum, Quantum Organic Chemistry (Interscience, New York, 1965).
V. M. Ivanov, M. G. Tsepkov, and V. N. Figurovskaya, Mosc. Univ. Chem. Bull. 65, 370 (2010).
S.-J. Yeh and H. H. Jaffe, J. Am. Chem. Soc. 81, 3283 (1959).
M. Isaks and H. H. Jaffe, J. Am. Chem. Soc. 86, 2209 (1964).
E. Stern and K. Timmons, Introduction to Electronic Absorption Spectroscopy in Organic Chemistry (Edward Arnold, London, 1970; Mir, Moscow, 1974), rus. p. 144.
M. B. Robin and W. T. Simpson, J. Chem. Phys. 36, 580 (1962).
Yu. A. Mikheev, L. N. Guseva, and Yu. A. Ershov, Russ. J. Phys. Chem. A 89, 224 (2015).
H. B. Gray, Electrons and Chemical Bonding (Benjamin, New York, 1965).
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Mikheev, Y.A., Ershov, Y.A. Structure of Dimers and the Nature of Color in 4′-Nitro-4-dimethylaminoazobenzene Solutions. Russ. J. Phys. Chem. 92, 286–294 (2018). https://doi.org/10.1134/S0036024418020164
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DOI: https://doi.org/10.1134/S0036024418020164