Design of photoactive molecular devices based on quantum chemical investigations of phenylenediamine, carbazole, tetracianoquinodimethane and benzene molecules

Jelena Tamuliene, Arvydas Tamulis, Mindaugas L. Balevicius*, Nick A. Kotov**
 Institute of Theoretical Physics and Astronomy, A. Gostauto 12, 2600 Vilnius, Lithuania,
Phone : 370-2-620861, Fax: 370-2-225361,
 *Faculty of Physics, Vilnius University,Sauletekio al. 9, III rumai, 2054 Vilnius, Lithuania
**Department of Chemistry, Oklahoma State University, Stillwater, Oklahoma 74078, USA
 
Quantum chemical ab initio design of photovoltaic elements and two variable logic functions of molecular digital computers are performing by using organic electron insulator, photo-induced electron donor and electron acceptor molecules and photoactive supermolecules.

 The quantum chemical calculations and investigations of benzene (Ph), carbazole (Cz), 7,7,8,8-tetracianoquinodimethane (TCNQ) and 1,4-phenylenediamine (PhDA) molecules were done using BPW91 and B3PW91 models of Density Functional Theory (DFT) in cc-pVTZ basis sets coded in Gaussian 94, Revision E. 2 with full geometry optimization. The calculations of molecular diode designed from mentioned above molecules and molecules of bridge -C2H2- were done using B3PW91 model in 6-311G basis set.

 As an example we present here that according BPW91/cc-pVTZ calculation HOMO and LUMO of C6H6 molecule are respectively equal to -0.230 a. u (-6.259 eV) and -0.040 a. u. (-1.089 eV) that confirm that the molecule is weak electronacceptor. HOMO and LUMO of PhDA molecule are equal to -0.164 a. u. (-4.463 eV) and 0.003 a. u. (0.082 eV) respectively that means that one is good electrondonor. The analysis of results of calculations showed that usage DFT B3PW91 and BPW91 methods in cc-pVTZ is acceptable for molecule geometry calculations and can be used for the design of new theoretically aided supermolecules which in future should be synthesised.

 The design of molecular photoactive diade PhDA-C2H2-Ph is done based on the analysis of quantum characteristics of benzene and PhDA molecules. The results of optimization of interatomic distances and angles of molecular insulator bridge -C2H2- showed that planes of PhDA and benzene molecule fragments are oriented by 1.177 and 1.923 degrees respectively the plane of the bridge fragment. Small negative charge equals to 0.031 e transfers from PhDA molecule fragment to the -C2H2- and benzene molecule fragments. There can expect that the electron charge should be transferred from PhDA fragment to benzene fragment during the diade excitation by light. The small charge transfer in ground state exists because of large value of condensed to bond all electrons between C atoms of bridge fragment. Calculations of the diade spectrum using configuration interactions single-excitation (CIS) Hartree-Fock method in 6-311G basis set in first excited state showed that the diade should be excited by wave length equals to 282.31 nm. This enables to use this molecular diade for the solar energy converters.

 Using our results of quantum chemical calculations were designed two supermolecules:

1) PhDA-C2H2-TCNQ-C2H2-TCNQ-C2H2-Cz and
2) Cz-C2H2-TCNQ-C2H2-Ph-C2H2-Ph-C2H2-PhDA.
Depending on the conditions of excitation and the outputing of transfered electron charge the 1) supermolecule might be Converse Unitary Negation-1, Converse Unitary Negation-0, Unitary Negation-1 or unitary Negation-0 two variable logic functions. The 2) supermolecule might be And, Nand, <<0>> as well as <<1>> Matrix Constants depending of the way of excitation and ouputing the transfered electron charge.

 Acknowledgements : Our research described in this article was supported by the Governments of Lithuania, U.S.A and France. A. Tamulis thanks J.-M. Nunzi for the invitation to CEA, Saclay. Authors thanks the Department of Chemistry, Oklahoma State University, Stillwater, Oklahoma 74078, USA for the allowance to use DEC-AXP-OSF/1 computer and installed here Gaussian 94 Revision E.2 package