MODELING OF ENERGETICAL PROPERTIES OF BIS-AZO COMPOUNDS. ROLE OF TAUTOMERIZATION Alytis Gruodis, Nurija Kelminskienė Department of General Physics and Spectroscopy, Vilnius university

Material 8th decade of XX century– electrophotographic dyes 1th decade of XXI century– molecular device (SC!) (in poled polymer matrix, 1MV/cm) Bisazo π-conjugated derivative – Stable, no photochemistry 2,7-diamino-fluorenone bisazo-pigmentum NA1, containing [-O-Me], EE,EQ,QQ conformers (tautomers) GU3, containing two [–Cl], EE,EQ,QQ conformers (tautomers).

NA1 (R=[-C6H4-OMe]) GU3 (R=[-C6H4Cl2]), where fluorenone is connected in position 2 and 7 via [-N=N-] bridge to quinine.

Main task Probable geometry of molecule in layered structures Explanation of experimental absorption spectrum Molecular energetics

Technique of modeling Quantum chemical methods Gaussian09 software 6/31G(d) basisset Optimization of molecular geometry Density functional B3LYP method Calculation of electronic excitation Semiempirical ZINDO method for singlets only Evaluation of charge redistribution Semiempirical TD method for siglets only

Intramolecular proton transfer Enol-Quinine tautomerisation Trans-cis transition Proton donor Proton acceptor

Second task How many different forms? EE, EQ, QQ ?

Two molecular motions 1) proton jump in tautomerization process allows the existence of both - hydrazone-quinine form (Q) and azo-enol form (E); 2) conformational rotation of quinine fragment allows the existence of partially ’broken’ pi-conjugated system: Generally, three type of different tautomers (EE, EQ, QQ) for NA1 and GU3 derivatives must be analyzed

Problem: EE, EQ, QQ ?

1. Geometry optimization Gaussian09 B3LYP/6-311G(d,p) opt

NA1

GU3

Optimization of geometry Three tautomiric forms: EE,EQ,QQ. Nine forms excluded EQ ir QQ – could be non-planar tautomers. Benzene derivatives ( [-O-Me] ir [–Cl]) are oriented by angle 60 deg

2. Electronic excitation Semiempirical ZINDO method STO-3G basis

Acid solution Basis solution

3. Charge redistribution What about CT state in region of 2 eV? Gaussian09, TD(singlets,nstate=6) HF/6-31G sp Charge redistribution between quinine, fluorenone and quinine, Derivatives R are not included ( partial skeleton redistribution)

Conclusions EQ form

Coexixtence of both: EE and EQ forms depending of the pH of media

Conclusions 1.Coexistence of both: EE and EQ forms depending of the pH of media 2.Fragmental rotation in range 30 deg (15 deg from equilibrium) like swinging. Excluding of band et 2 eV from 40 deg. 3.Partially broken pi-conjugated system 4.CT transition for EQ form

Thank you for attention