Nenad Trinajstić (26 October 1936 – 27 August 2021) was a Croatian chemist and one of pioneers of the chemical graph theory.
From 1968 to 1970 he was a Postdoctoral fellow under Michael J. S. Dewar at the University of Texas, Austin with whom he has published 16 papers.
He wrote the first monograph on chemical graph theory[3] and introduced several molecular descriptors such as 3-dimensional Wiener index[4] and Zagreb indices (with Ivan Gutman),[5] which are among the more studied topological indices.
Independently of Jun-ichi Aihara, he introduced topological resonance energy as a reliable theory of aromaticity.
[6][7] In quantum chemistry he worked on semi-empirical molecular orbital theory and settling conjugated-circuit model on a firm quantum-mechanical basis.