MODELING OF ENERGETICAL PROPERTIESOF BIS-AZO COMPOUNDS.

ROLE OF TAUTOMERIZATIONAlytis Gruodis, Nurija Kelminskienė

Department of General Physics and Spectroscopy, Vilnius university

Material

8th decade of XX century– electrophotographic dyes1th 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 geometryDensity functional B3LYP method

Calculation of electronic excitationSemiempirical 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 excludedEQ ir QQ – could be non-planar tautomers.

Benzene derivatives ( [-O-Me] ir [–Cl]) are oriented by angle 60 deg

2. Electronic excitation

Semiempirical ZINDO methodSTO-3G basis

Acid solutionBasis solutionBasis 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)

ConclusionsEQ 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