3-Input AND Molecular Logic Gate with Enhanced Fluorescence Output: The Key Atom for the Accurate Prediction of the...

The development of artificial receptors for sensing and recognition of species, as well as for advanced logic functions, is a significant challenge in the field of molecular information technology. Here, we study theoretically, via DFT/TD-DFT calculations, the photophysical properties of a 3-input AND molecular logic gate which presents an enhanced fluorescence spectrum. It was found that the geometry conformation at an N atom of the piperazine group is the key factor for the correct calculation of the absorption spectra of the calculated structures. Its geometry is between tetrahedral and planar, while changes in the corresponding CNCC dihedral angle of about 10 degrees can cause significant shifts of the main peak of the absorption spectra up to 100 nm. Moreover, the unusually enhanced fluorescence of a molecular logic gate (MLG) is explained. Finally, we conclude that molecular systems having N atoms, whose geometry is between planar and tetrahedral, can be ideal molecules as sensors and molecular logic gates. Our calculated absorption and emission spectra are in excellent agreement with available experimental data.