Electropolymerization of Pd(II) Complexes Containing Phosphinoterthiophene Ligands

Abstract

A series of Pd complexes of 3'-diphenylphosphino-2,2':5'2' '-terthiophene (1a, dppterth) in which the metal is coordinated in three different modes have been prepared and electropolymerized, resulting in the formation of conductive thin films. In [Pd2(mu-Cl2)(dppterth-P,C3)2] (3a) the metal is P,C-coordinated, in [PdCl2(dppterth-P)2] (4a) the coordination is monodentate via the phosphine, and in [Pd(dppterth-P,C3)(dppterth-P,S1)][PF6] (5a) both P,C- and P,S-coordination modes are found. In 5a, the coordinated thiophene is hemilabile and may be displaced by reaction with more strongly coordinating ligands such as isocyanides. To probe the effect of blocking the alpha-position of the terthienyl moiety with methyl groups, 3'-diphenylphosphino-5-methyl-2,2':5'2' '-terthiophene (1b, Me-dppterth) and 3'-diphenylphosphino-5,5' '-dimethyl-2,2':5'2' '-terthiophene (1c, Me2-dppterth) were prepared, and the corresponding series of Pd complexes was synthesized. One of these complexes, [Pd(Me2-dppterth-P,C3)(Me2-dppterth-P,S1)][PF6] (5c), has been crystallographically characterized. The electropolymerized films prepared from 5a react with isonitriles, and shifts in the absorption spectra of the electropolymerized materials are observed upon reaction. A Pd complex has also been prepared from 5-diphenylphosphino-2,2':5'2' '-terthiophene (2, 5dppterth), and this complex has been electropolymerized. All the electropolymerized thin films have been characterized using EDX analysis, which demonstrates good correspondence with the elemental analysis of the respective monomers, and the maximum conductivities of the films are near 10(-4) S x cm(-1). Comparing the electropolymerization behavior of the complexes, along with their electrochemical and spectroscopic data, allows conclusions to be drawn regarding the involvement of pi-delocalization and the metal group in the conductivity of the materials.

Sterics versus Electronics: Regioselective Cross‐Coupling of Polybrominated Thiophenes

“…To demonstrate the power of the new regioselective methods, they were applied to the synthesis of the known compound 4Ј-bromo-5-methyl-2,2Ј;5Ј,2"-terthiophene (16) [20] from thiophene (Scheme 1). By the new methods, the total number of steps was reduced from six to three, and the overall yield increased from 15 to 43 %.…”

Functional Oligothiophenes: Molecular Design for Multidimensional Nanoarchitectures and Their Applications

“…395,396 The presence of cis-and trans-isomers has been comfirmed from 31 P NMR specroscopy. Electropolymerization of these complexes showed large electronic interactions between Pd moieties and the polythiophene backbone, which produced an increase in conductivity of the polymer film.…”

S· · ·S Interaction in Pd(II) Complexes of Bis(phosphino)oligothiophene with Various Substituents

“…These bond lengths are comparable to those which are previously reported in other complexes of this type. 11 The C-S bond lengths are not equal in oligothiophene due to coordination of two rings with P atom at one α-position. It has also been suggested that enhanced π-back bonding with coordinated thiophene ring would weaken the C-S bond.…”