Theoretical Investigations Of Optical And Electronic Property Of π-stacked Molecules

It is acknowledged that the π-π interactions play a key role in structural arrangements and molecular assemblies, including organic host-guest chemistry, molecular/biology, supramolecular chemistry and crystal packing. The structures of DNA, RNA, and proteins are stabilized by π-π interactions, and it has been estimated that around60%of aromatic side chains in proteins have π-π interactions. Currently, much interest is devoted new generations of plastic electronic devices such as field-effect transistors (FET), light-emitting diodes (LED), or photovoltaic and solar cells. In fact, tuning π-π interactions between aromatic rings via molecular design is key technique for achieving high-performance organic devices. However, intramolecular supramolecular molecules have been neglected in the past two decades since the discovery of DNA with the intramolecular π-stacked motifs. Until now, intramolecular π-stacked polymers have exhibited unique nonvolatile flash memories and magnetic resistance properties in organic electronics. Besides, intramolecular π-stacked systems have also been designed for the detector of explosive TNT, n-type semiconductors, and offer an effective channel for triplet energy transfer, charge transport and excimer emissions. By far, however, the researches about intramolecular π-π stacking are not enough. To further gain insight into intramolecular π-π interactions and the structure-function relations, we here designed and studied three series of molecules containing intramolecular π-π stacking. Part1:Theoretical investigation of optical and electronic property of fluorene-based and4.5-diazafluorene-based π-stacked molecules. Part2: Theoretical investigation of the piezochromic behavior of Cross-Anthracenes. Part3:Theoretical investigation of optical and electronic property of sulfur-[n]helicenes and [n]helicenes. An integrated approach has been employed to estimate the relevant parameters for optical and electronic property such as internal reorganization energies (λ), ionization potential (IP), electronic affinity (EA) and frontier molecular orbitals, NCI analysis. The absorption and fluorescence spectra of these materials were also predicted and discussed. Through a comprehensive analysis, we hope to find the structure-functions relations and guide to design new materials in new areas.