SYNTHESIS OF NOVEL BIPYRIDINE AND TERPYRIDINE LIGANDS … · et Biochimie Pharmacologique ... Xyl, 140°C, 24 h Cl2Pd(PPh3)2 5% PPh3 10% N N N N SnBu31 eq. Cl 65 % Cl Cl Xyl, 140°C,

www.davidmartineau.net [email protected]

David Martineaua, Marc Beleya and Philippe Grosb

aLIMBP - IPEM, 1 bd Arago, Technopôle Metz 2000, 57070 Metz, France. [email protected], [email protected] - UMR 7565, Faculté des Sciences et Techniques, BP 239 bd des Aiguillettes, 54506 Vandoeuvre-les-Nancy, France. [email protected]

Upcoming next generation solar cells based upon organic dyes are in first line for the replacement of polluting energy sources that currently destroy our planet. These Dye Solar Cells (DSC) rely on the absorption of light by an organic photosensitizer that transfers electrons to a TiO2 nanocrystaline matrix.

It is well know that RuII complexes containing terpyridine ligands act like very efficient photosensitizers. Therefore, the synthesis of new complexes containing novel terpyridines represent a way to improve photo-electrical conversion involved in DSC.

Several works demonstrate that Small Molecule OLED (SMOLED) can be obtained with RuII complexes containing bipyridines. Next challenge is to vary complexes emission spectra for use in true colors displays that require at least RGB light sources.

The HOMO-LUMO gap is responsible of complexes photophysical properties. To play with this energy gap, we decided to investigate the preparation of novel bipyridine and terpyridine ligands having different electronic behaviors.

A pyridine starting pattern bearing either an electro-releasing or an electro-attracting group on the C-4 position is functionalized via the setup of regioselective lithiation methods using nBuLi-Li-N,N-dimethylaminoethanolate (Buli-LiDMAE) aggregated system to lead to halogenated and organometallic building blocks.

A method to operate lithiation of the 4-pyrrolylpyridine pattern as been developed with nBuLi-LiDMAE. Moreover, iterative lithiation allows to obtain 2,6 difunctional building blocks.

Pyrrolyl group was chosen for its strong electro-donor property and could then induce an improved destabilization of RuII if present on ligands.

Novel bipyridines and terpyridine have been synthesized from the 4-pyrrolylpyridine building blocks using homocoupling or Stille cross-coupling reactions.

Prepared complexes demonstrate efficient and growing absorption according to the number of pyridyl and pyrrolyl that compose the ligands. As expected, complexes containing L1 or L2 bipyridines are emitting light at 635 and 655 nm.

Corresponding RuII complexes were successfully synthesized under microwave irradiation whereas same reaction in refluxing DMF led to incomplete complexation.

Synthesize ligands bearing both carboxyl and pyrrolyl groups. And develop tin-free coupling reactions.

Take advantage of the limitation of solvent refluxing complexation to prepare heteroleptic complexes mixing carboxylated ligands and our polypyridines to induce a push-pull effect on metal electrons.

Explore electropolymerization observed with [Ru(L3)2],2PF6 that could possibly lead to interesting photosensitized polymers.

Realize the study of other patterns to synthesize more novel ligands and complexes. Try to replace RuII with cheaper metal such as FeII, ZnII, CuII, NiII...

First investigations of the 4-pyrrolidylpyridine pattern are very promising.

Nowadays fashion screens are flat. Unlike LCD screens that require back-lighting, OLED displays offer self luminating pixels for less power consumption and low cost effective production with theoretically no limit of size or flexibility.

SYNTHESIS OF NOVEL BIPYRIDINE AND TERPYRIDINE LIGANDS FOR THE PREPARATION

OF PHOTOACTIVE COMPLEXES

Photosensitizer for DSC appliance

Step 1 :

Studies of the 4-pyrrolylpyridine pattern

The newly obtained ligands are then complexed to a selected transition metal (usually RutheniumII) through a fast microwave irradiation process that overcomes limitations of classical solvent refluxing conditions. Again, it is possible to mix different ligands to also prepare heteroleptic complexes.

Once these new complexes are prepared, multiple photophysical and electrochemical studies are performed in order to evaluate their possible efficiency in applications presented above.

Step 3 :

Thus prepared building blocks are engaged in coupling reactions. In such a way, C-2 substituted blocks lead to bipyridines and the use of both C-2 and 2,6 disubstituted ones lead to terpyridines. Furthermore, different C-4 functionalized pyridine starting patterns can be combined to offer a wide range of ligands demonstrating a smooth transition between electro-releasing and electro-attracting properties.

Step 2 :

Luminophore for SMOLED and flat screens

LIMBPLaboratoire d’Ingénierie Moléculaire

et Biochimie Pharmacologique

Synthèse Organométallique et Réactivité

> Interest of photoactive complexes for nanotechnologies :

>> Synthetic strategy :

>>> First results and perspectives :

N

N

N

N

N

N

RuII

hν

hν hν

hν

N

N

N

RuII NCS

NCS

NCS

O

O

O

O

O

O

e-

TiO2

hν

D

N

FGa

N

FGa

A

N

FGb

N

FGb

A

N N

N

N N

FGa FGa,b

FGa,b

FGa

FGa,b

N

FGa

A

N

FGb

A

A

A

[Mn(bpy)3],nPF6

[Mn(tpy)2],nPF6

TiO2 hν

N

N

N

RuII

O

O

O

O

O

O

N

N

N

N

C-4 substituted pyridinestarting patterns

C-2 and C-6 functionalbuilding blocks bipyridine or terpydine assembly tris-bipyridine or bis-terpydine complexes

1 2 3

Perspectives

N

N

N

N

Li

nBuLi - LiDMAE3 eq.

Toluene / 1h / -78°C Toluene / -78°C, rtN

N

A

Electrophile3.5 eq.

N

N

N

N

Li

nBuLi - LiDMAE3 eq.

Toluene / 1h / -78°C Toluene / -78°C, rtN

N

A

Electrophile3.5 eq.

AA A

A = SMe 90%Cl 76%Br 60%

I 60%PPh2 80%

SnBu3 50%

A = SMe 75%Cl 95%

abs.

0

0,5

1

1,5

2

2,5

3

3,5

4

325 375 425 475 525 575 625

nm

[Ru(L1)3],2PF6

[Ru(L2)3],2PF6

[Ru(L3)2],2PF6

UV-Vis absorption spectra

N

N

Xylene, 140°C, 24 h

Cl2Pd(PPh3)2 5%PPh3 10%

N

N

N

N SnBu3 1 eq.

Cl

65 %

N

N

DMF, 50°C, 1h30

NiCl2, 1,1 éq. PPh3 , 4,4 éq.Zn°, 1,1 éq.

N

N

NCl

N

70 %

N

N

Xyl, 140°C, 24 h


N

N

N

N SnBu3 1 eq.

Cl

65 %

ClCl

Xyl, 140°C, 24 h


N SnBu3 1 eq.

N

N

N

40 %

N

L1

L2

L3

N

N

N

O

OH

N

N

NN

O

OH

O

OH

N

N

N

N

Li

nBuLi - LiDMAE3 eq.

Hexane / 1h30 / 0°C Hexane/ -78°C, rtN

N

A

Electrophile3.5 eq. A = SMe 70%

Cl 79%Br 62%

[Ru(L1)3],2PF6 98 %

λmax = 465 nm in acetonitrile

φem = 0.022 %

E1/2 ox. (RuIII/RuII)= 1,16 V / SCE

[Ru(L2)3],2PF6 95 %


φem = 0.044 %

E1/2 ox. (RuIII/RuII)= 1,12 V / SCE

[Ru(L3)2],2PF6 96 %


E1/2 ox. (RuIII/RuII)= 1,18 V ref. SCE

3 + RuCl3 + RuCl3+ RuCl33 2

N

N

NN

NN

NN N

Ru , 2PF6

N

N

NN

NN

N

N

N

N

N

N

Ru , 2PF6

N

NN

NN

N

N

N

Ru , 2PF6

N

N

N

N

N

N

N

N

N

NN

i) 300 W microwaves, 3 mins,NEM, 2 dropsii) KPF6 treatment.



N

N N N N

N

N N

RuII

N

N

N

R

N

NNHN *

Cpx Cpx

Cpx

= Cpx

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DE LA RECHERCHE

SCIENTIFIQUE

Documents

SYNTHESIS OF NOVEL BIPYRIDINE AND TERPYRIDINE LIGANDS … · et Biochimie Pharmacologique ... Xyl, 140°C, 24 h Cl2Pd(PPh3)2 5% PPh3 10% N N N N SnBu31 eq. Cl 65 % Cl Cl Xyl, 140°C,