Protonation in Heteronuclear Diatomic Molecules: Same Molecule, Different Proton Affinities


  • Emmanuel E. Etim Federal University Wukari, PMB 1020, Wukari, Taraba State, Nigeria
  • Oko Emmanuel, Godwin Federal University Wukari, PMB 1020, Wukari, Taraba State, Nigeria


Protonation, Heteronuclear, Diatomic, Proton affinity PA, Computational methods.


Communication in Physical Sciences 2020, 6(2):835-844

Authors: Emmanuel E. Etim* Oko Emmanuel, Godwin and Sulaiman Adeoye Olagboye

Received 22 March 2020/Accepted 28 December 2020

Every heteronuclear diatomic molecular species has two possible sites for protonation giving rise to two possible proton affinity values for a single molecule but experimentally only one proton affinity value is measured for each molecular species with no information regarding where the proton is attached in the molecule. This present work aimed at calculating the proton affinity (PA) of heteronuclear diatomic molecules, specifying which site favors protonation and observing common and rare trends in proton Affinity. In this work, quantum chemical calculations were employed to calculate PA of nitrogen (I) oxide, oxygen monofluoride, carbon(ii)oxie, phosphorus monoxide, silicon(II)oxide, silicon monosulfide, phosphorus mononitride, carbon monosulphide,  and phosphorus monosulfide. The indicated that in the heteronuclear diatomic molecules, the best site of protonation corresponds to the most stable protonated analogue, the experimentally assigned value also corresponds to the most stable protonated analogue. These results also aid in indicating the possible factors which could influence the best site of protonation such as  bonding nature, stability of the protonated analogue, electron density/electronegativity  and Periodic trend.


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Author Biographies

Emmanuel E. Etim, Federal University Wukari, PMB 1020, Wukari, Taraba State, Nigeria

Department of Chemical Sciences,

Oko Emmanuel, Godwin, Federal University Wukari, PMB 1020, Wukari, Taraba State, Nigeria

Department of Chemical Sciences


Emsley, J. (1989). The Elements. Oxford: Clarendon Press, UK. pp. 22–23.

Whitten, K. W.; Davis, R. E.; Peck, M. L; Stanley, G. G. (2010). Chemistry (9th ed.). Brooks/Cole, Cengage Learning. pp. 337–338.

Riccardo, F., (1971) Bonding properties of diatomic molecular orbitals. Journal of Physical Chemistry, 75, 19, pp. 3012-3014. DOI: 10.1021/J100688a024

Taoyi, C., & Thomas, A. M. (2019). Bond orders of the diatomic molecules. RSC Advances, 9, pp. 17072-17092.

Castro, M., Keller, J., & Mareca, P., (1991). Bonding in heteronuclear transition metal diatomics: Nblr. International Journal of Quantum Chemistry, 39, 5, pp 649-754.

Pauling, L. (1939). Nature of the chemical bond. Cornell University press, Ithaca, 1939, p.70

Tennnyson J. &Yurchenko S. N. (2012). ExoMol:molecular Line Lists for exoplanet and otheratmospheres. Mon. Not. R. Astron. Soc. 425, 1, pp. 21-33.

Etim E. E., Chrisanthus A., Usman L., Ifeoma Sandra U. & Etiowo George Ukpong, (2020a) Protonation of carbonyl sulphide: Ab-initio. Journal of Applied Sciences, 20, pp. 26-34

Johns-Krull C. M., Valenti J. A. & Koresko C., (1999), Measuring the Magnetic Fieldon the Classical T Tauri Star BP Tauri Astrophysics Journal, 516, pp. 900-915.

Brezinsek, S., Stamp, M. F., Nishijima, D., Borodin, D., Devaux, S., Krieger, K., Marsen, S., O'Mullane, M., Bjoerkas, C/. & Kirschner A. (2014). Study of physical and chemical assisted physical sputtering of beryllium in the JET ITER-like wall. Proceeding of IAEA Technical Meeting on energetic particles in magnetic confinement systems, Peking, China.

Vallon R.; Ashworth S.H.; Crozet P.; Field R.W.; Forthomme D.; Harker H.; Richard C.; & Ross A.J.;(2009). Room-temperature metal-hydride discharge source, with observations on NiH and FeH. Journal of Physical Chemistry,. A 113, pp.13159-13166.

Chan M. C., Yeung S. H., Wang N. & Cheung A. S. C. (2013). Laser absorption spectroscopy of the d3Πg ← c3Σu+ transition of C2. Journal of Physical Chemistry, A 117, pp. 9578-9583.

Nozaki, Y., Kongo K., Miyazaki, T., Kitazoe M., Horii, K., Umemoto, H., Masuda, A. & Matsumura, H. (2000). Identification of Si and SiH in catalytic chemical vapor deposition of SiH4SiH4 by laser induced fluorescence spectroscopy. Journal of Applied Physics, 88, pp. 5437-5443.

Johnson E.R.;(1965). Twilight resonance radiation of AlO in the upper atmosphere. Journal of Geophysical Research, 70, pp. 1275-1277.

Gole J. L. & Kolb C. E. (1981). On the upper atmospheric chemiluminescent emission observed upon release of aluminum vapor and its compounds. Journal of Geophysical Research: Space Physics, 86, pp.9125-9136.

Knecht D.J.; Pike C.P.; Murad E.; Rall D.L.A.; (1996). Interaction of solid-rocket exhaust with the atmosphere. Journal of Spacecraft and Rockets, 33, pp. 677-685.

Coker, J. (2015) Applications of diatomic molecules; Ph.D Dissertation, University of Oklahoma Graduate College.

Vvedensky D. D. (2017) Encyclopedia of spectroscopy and spectrometry (Third Edition), Elsevier, 978-0-12-803224-4. https;// 1016/B978-04442227-6/50005-3

Zumdahl, S. S. (1986) Chemistry. Lexington, MA: Heath. ISBN 0-669-04529-2.

Adam M., Kevin R., Darrin M. Y (2010). Accurate proton affinity and gas-phased basicity values for molecules important in biocatalysis. Journal of Physical Chemistry B.114, 43, pp. 13911-13921

Longuet-Higgins H.C.,(1956) Proton affinities, recueil des Travaux Chimiques des Pays-B, Volume 75, issue 7. recl.19560750718

Frisch, M.J.; Toucks, G.W.; Schlegel, H.B.; Scuseria G.E.; Robb, M.A.; Cheeseman, J.R.; Scalmani, G.; Baron, V.; Mennucci, B.; Peterson, G.A., (2009) Gaussian 09 revision D.01; Gaussian, Inc., Wallingford, CT.

Etim, E. E., Oko, G. E., Onen, A. I., Ushie O. A., Andrew, C., Lawal, U. & Khanal, G. P. (2018). Computational Studies of Sulphur trioxide (SO3) and its protonated analogues. Journal of Chemical Society of Nigeria, 43, 2, pp 10-17

Etim, E. E., Chrysanthus, A., Lawal, U., Ifeoma, S. U. & Etiowo, G. U. (2020b). Protonation of Carbonyl Sulfide: Ab-initio study. Journal of Applied Sciences, 20, pp. 26-34

Etim, E. E. & Arunan, E.,(2016). Interstellar isomeric species, energy, stability and abundance relationship. European Physics Journal.Plus, pp. 131, 12, -8-0

Etim, E. E., Abah, B. S., Mbakara, I. E., Inyang, E. J. & Ukafia, O. P. (2017) Quantum Chemical Calculations on Silicon Monoxide (SiO) and its Protonated Analogues. Tropical Journal of Applied Natural Sciences, 2, pp. 61-68..

Etim, E. E., Sulaiman, A. O., Oko, E. G. & Irene M. A., (2020c) Quantum Chemical studies on Silicon tetrafluoride and its protonated analogues. International Journal of Modern Chemistry, 12, 1, pp 26-45.