Experimental and theoretical study of monosubstituted guanidines by vibrational spectroscopy Part 1.—Structure of cyanoguanidine

Abstract

We have recorded and analysed IR absorption and Raman spectra of cyanoguanidine C₂N₄H₄ (CG) in different physical states (crystalline, solutions and composition with porous glasses). Co-existence of two different structural CG species: cyanoimine I and cyanoamine II with conjugated and isolated multiple bonds, respectively, is shown. The ratio of structure I to structure II can be varied using a porous glass technique. Density functional calculations (B-LYP/6-31G*) of the optimal structure and vibrational frequencies of CG confirm that cyanoimine and cyanoamine co-exist. We suggest that the X-ray diffraction data showing equivalent C–N and C=N bond lengths in the guanidine fragment is a consequence of superposition of both tautomers that are present simultaneously in CG samples.

References

1. F. Pohl, J. Prakt. Chem., 1908, 77, 533.
2. E. Bamberger, Ber., 1883, 16, 1074.
3. B. I. Sukhorukov and A. I. Finkelshtein, Opt. Spektrosk., 1959, 6, 637 (in Russian).
4. A. E. Kretov, Usp. Khim., 1954, 23, 105 (in Russian).
5. J. M. Adams, Acta Crystallogr., Sect. B, 1977, 33, 1513.
6. J. H. Bryden, J. A. Burkadt and E. W. Hughes, Acta Crystallogr., 1956, 9, 573.
7. F. L. Hirshfeld and H. Hope, Acta Crystallogr., Sect. B, 1980, 36, 406.
8. A. D. Becke, Phys. Rev. A, 1988, 38, 3098.
9. C. Lee, W. Yang and R. G. Parr, Phys. Rev. B, 1988, 37, 785.
10. B. G. Johnson, P. M. W. Gill and J. A. Pople, J. Chem. Phys., 1993, 98, 5612.
11. E. B. Burgina, V. P. Baltakhinov, E. V. Boldyreva and A. V. Arbuznikov, J. Mol. Struct., submitted.
12. A. V. Arbuznikov, L. A. Sheludyakova and E. B. Burgina, J. Mol. Struct., submitted.
13. A. D. Becke, J. Chem. Phys., 1993, 98, 1372; 5648.
14. W. J. Hehre, R. Ditchfield and J. A. Pople, J. Chem. Phys., 1972, 56, 2257.
15. GAUSSIAN 92/DFT, Revision G.2, M. J. Frisch, G. W. Trucks, H. B. Schlegel, P. M. W. Gill, B. G. Johnson, M. W. Wong, J. B. Foresman, M. A. Robb, M. Head-Gordon, E. S. Replogle, R. Gomperts, J. L. Andres, K. Raghavachari, J. S. Binkley, C. Gonzalez, R. L. Martin, D. J. Fox, D. J. Defrees, J. Baker, J. J. P. Stewart and J. A. Pople, Gaussian, Inc., Pittsburgh PA, 1993.
16. A. S. Davydov, The Theory of Molecular Excitones, Nauka, Moscow, 1968(in Russian).
17. P. P. Shorygin, Zh. Fiz. Khim., 1947, 21, 1125 (in Russian).
18. E. V. Sobolev and L. A. Sheludyakova, in 12th European Crystallogr. Meeting, Abstracts, Moscow, USSR, 1989, p. 320.
19. L. A. Sheludyakova, E. V. Sobolev and L. I. Kozhevina, Zh. Prikl. Spektrosk., 1991, 55, 53 (in Russian).
20. A. V. Arbuznikov, L. A. Sheludyakova and E. B. Burgina, Chem. Phys. Lett., 1995, 240, 239.
21. A. A. Radtsig, B. M. Smirnov, Handbook on Atomic and Molecular Physics, Atomizdat, Moscow, 1980(in Russian).