Slide 1

Perugia - 15 Giugno 2007 VI Convegno Nazionale sulla Scienza e Tecnologia dei Materiali Tetraarylcyclosiloxane Rings as Scaffolds for Second Order NLO Active and Photoluminescent Materials Alessio Orbelli Biroli, Marco Ronchi, Maddalena Pizzotti, Renato Ugo, Elena Lucenti, Marco Cavazzini, Silvio Quici Slide 2 SiO 2 Introduction Slide 3 Which model? = ?= ? The cyclooligosiloxanolates of general formula [RSi(O)O] n n- (R = Ph; n = 3, 4, 6 ) could represent a good 2D-model for a monolayer of organic chromophores bound to a silica-based surface.* * Pozdniakova, Yu. A.; Lyssenko, K. A.; Korlyukov, A. A.; Blagodatskikh, I. V.; Auner, N.; Katsoulis, D.; Shchegolikina, O. I. Eur. J. Inorg. Chem. 2004, 1253-1261 Slide 4 Which model? These molecules can be considered as building blocks for supramolecular architectures on which NLO active or photolumiescent organic cromophores are covalently bound in order to create an organized nanostructure that allows to study the molecular-level features of a monolayer linked to the silica surface. Slide 5 Synthesis of tetraarylcyclosiloxane rings X = Cl, Br, CH=CH 2, CH 2 Cl For this reason we have synthetized a series of sodium tetraarylcyclosiloxanolates and their trimethylsiloxy derivatives of general formula [4-X-C 6 H 4 Si(O)OR] 4 (R=Na, SiMe 3 X = Cl, Br, CH 2 Cl, CH=CH 2 ) properly functionalized in the para position of the aromatic rings. yield 40-80% yield 40-70% - solubility in organic solvents - stability of the Si-O-Si bound M. Ronchi, M. Pizzotti, A. Orbelli Biroli, P. Macchi, E. Lucenti, C. Zucchi, J. Organom. Chem., 2007, 692, 1788-1798 Slide 6 P. Macchi 2006 X-ray structure of [p-BrC 6 H 4 Si(O)OSiMe 3 ] 4 Slide 7 Linear opticsNon linear optics (NLO) Input wave Output waveInput waveOutput wave molecule (Laser) electron withdrawing group -conjugated bridge electron donor group push-pull molecule V/cm (laser) Slide 8 Synthesis of the models for second order NLO The tetraarylcyclosiloxane rings have an active function as electron withdrawing group. yield: 23% yield: 35% Slide 9 yield: 47% Synthesis of models for second order NLO The tetraarylcyclosiloxane rings have an active function as electron withdrawing group. Slide 10 NLO response of nanoorganized chromophores compound EFISH 10 -48 (esu) (1.91 m) (solvent CHCl 3 ) (D) 10 -30 (esu) 1989.0022 83910.5380 (780)11.30(69) compound EFISH 10 -48 (esu) (1.91 m) (solvent CHCl 3 ) (D) 10 -30 (esu) 683.0822 3183.6487 783.9620 Slide 11 Si-gruop vs. nitro-group as EWG compound EFISH 10 -48 (esu) (1.91 m) (solvent CHCl 3 ) (D) 10 -30 (esu) 683.0822 3183.6487 783.9620 compound EFISH 10 -48 (esu) (1.91 m) (solvent CHCl 3 ) (D) 10 -30 (esu) 275 (*) 5.5 (*) 50 (*) 482 (*) 6.6 (*) 73 (*) 281 (*) 6.1 (*) 46 (*) * Cheng, L.-T.; Tam, W.; Stevenson, S. H.; Meredith, G. R. J. Phys. Chem. 1991, 95, 10643-52 Slide 12 Synthesis of models for second order NLO The cyclotetrasiloxanic ring has a passive function as a simple scaffold. yield: 46% Slide 13 NLO response of nanoorganized chromophores compound EFISH 10 -48 (esu) (1.91 m) (solvent CHCl 3 ) 2600 (10 -3 M) 8100 (10 -4 M) 10000 (5 10 -5 M) 1260 (10 -3 M) 3400 (10 -4 M) 3400 (5 10 -5 M) Slide 14 SHG response by corona-poling measuraments The fall of SHG signal after the removal of the electric field is of 43% -43% Slide 15 Synthesis of models for photoluminescent materials yield: 10% Slide 16 Spectroscopic studies F in CH 2 Cl 2 solution : 12% F in solid state : 9% Decay exponential with lifetime 300ps Slide 17 Spectroscopic studies F in CH 2 Cl 2 solution : 6.5% F in solid state :