Understanding of molecular functions: Computational approaches

Accurate quantum computational chemistry has evolved dramatically. The size of molecular systems, which can be studied accurately using molecular theory, is increasing very rapidly. Theoretical chemistry has opened up a world of new possibilities. It can treat real systems with predictable accuracy. Computational chemistry is becoming an integral part of theoretical and experimental research in chemical science. In this paper, we will review our recent developments in the theoretical and computational study on some very interesting subjects such as fluorescent fluoride sensor, "on-off" molecular switch, electron transport through π-stacking, and molecular electronic device on the basis of the molecular functional levels. We provide a brief introduction about the importance of all these systems in the present scenario of scientific activity and the numerical results and discussion in the light of experimentally found results. We have enjoyed good progress in each of the above areas. We are very excited about our discoveries in each field and would like to share this enthusiasm with readers.