In this article we summarize the study of the electronic states and electron-vibrational interactions in squareplanar molecular entities playing the role of molecular cells in quantum cellular automata (QCA), a promising paradigm of quantum computing. The following issues are shortly discussed: 1) QCA as a paradigm of quantum computing; 2) molecular implementation of QCA; 3) vibronic coupling as the origin of charge trapping, encoding of binary information 4) non-linear cell-cell response; 4) spin-switching in molecular QCA based on mixed-valence cells; 5) multimode dynamic vibronic problem, the symmetry assisted approach.