Synthesis and Electron Transfer Studies of Ruthenium−Terpyridine-Based Dyads Attached to Nanostructured TiO₂

Abstract

A series of bis(terpyridine)RuII complexes have been prepared, where one of the terpyridines is functionalized in the 4'-position by a phosphonic or carboxylic acid group for attachment to TiO2. The other is functionalized, also in the 4'-position, by a potential electron donor. In complexes 1a, 3a, and 4a,b, this donor is tyrosine or hydrogen-bonded tyrosine, while in 2a it is carotenoic amide. The synthesis and photophysical properties of the complexes are discussed. On irradiation with visible light, the formation of a long-lived charge-separated state was anticipated, via primary electron ejection into the TiO2, followed by secondary electron transfer from the donor to the photogenerated RuIII. However, such a charge-separated state could be observed with certainty only with complex 2a. To explain the result, quantum chemical calculations were performed on the different types of complexes.

Self‐Assembly of Supramolecular Architectures and Polymers by Orthogonal Metal Complexation and Hydrogen‐Bonding Motifs

“…4'-(2-Furyl)-2,2':6',2''-terpyridine was obtained from 2-acetylpyridine and 2-furaldehyde as described by Constable et al [35] Oxidation by KMnO 4 [36] leads to 2,2':6',2''-terpyridine-4'-carboxylic acid (2). 5-Amino-N,N'-bis[6-(3,3-dimethylbutyrylamino)pyridin-2-yl]isophthalamide [5] (Hamilton amine 3), 6-aminohexanoic acid methyl ester hydrochloride (4), [37] diethyl 2,5-didodecyloxyterephthalate (11), [20,21] 2,5-didodecyloxyterephthalic acid (12), [20,21] [RuA C H T U N G T R E N N U N G (DMSO) 4 ]Cl 2 , [23] and [PtA C H T U N G T R E N N U N G (DMSO) 2 Cl 2 ] [38] were prepared as described in the literature; syntheses of 1-(6-hydroxyhexyl)-1,3,5-triazine-2,4,6-trione) (13) [19] and di-tert-butyl 4-(3-tert-butoxy-3-oxopropyl)-4-[6-(2,4,6-trioxo-1,3,5-triazinan-1-yl)hexanamido]heptanedioate (8) [12] were previously reported by us.…”

Interfacial Electron Transfer Dynamics of Two Newly Synthesized Catecholate Bound RuII Polypyridyl‐Based Sensitizers on TiO2 Nanoparticle Surface – A Femtosecond Pump Probe Spectroscopic Study

“…Several molecular dyads have been studied in this context. [19][20][21][23][24][25][26][27][28][29]69,70] Phenolic donor groups have been explored as an electron-donating functionality, in particular by Sundstrom et al [30,31,71] Most of these studies have been carried out on the nano-and microsecond timescales. To understand the influence of the electron-donating moiety it is important to study and compare the ET dynamics for 5, 6 and 7 on the ultrafast timescale.…”

“…[19][20][21][22][23][24][25][26][27][28][29] Much work has been carried out on systems where a secondary redox couple based on phenol has been used to rereduce the Ru III created by excited state electron transfer to nanoparticulate TiO 2 analogous to electron transfer from Tyr z to P 680 in photosystem II. [30,31] However, most of this work has been carried out with sensitizers based on carboxylate anchoring groups, which have certain disadvantages. Due to the low pK a of carboxylates (pK a ≈ 3.5) [32,33] there remains a possibility of slow desorption of the sensitizer dye molecules from the surface of semiconductor in the presence of water.…”

Ruthenium(II) Complexes of Carboxylated Terpyridines and Dipyrazinylpyridines

“…[13] A third preparation used a process similar to ours (49 % yield) and converted H1 to neutral, zwitterionic Ru(1) 2 (66 % yield), [3] the pentahydrate of which was characterized by using crystallography. Finally, the ligand has been prepared by base hydrolysis (93 % yield) [14] of the methyl ester, itself obtained in two steps (15 % yield), [15] and incorporated into a heteroleptic Ru II species. We had earlier prepared both homo-and heteroleptic Ru II complexes of H1 by KMnO 4 oxidation of the corresponding homoleptic 4Ј-(p-tolyl) complex, albeit as a mixture requiring chromatography, in low yields of each, and in an incompletely characterized state.…”

“…[3] Heteroleptic Ru II complexes of H1 have also been described. [2,14] In this work, we used a one-pot synthesis of H1 at room temperature from 2-acetylpyridine and 4-carboxybenzaldehyde (the ethyl ester of which can be used just as well) in the presence of KOH and NH 4 OH in aqueous MeOH (Scheme 1), a process that we have previously used to prepare several 4Ј-substituted terpyridines and dipyrazinylpyri-dines. [9,10,16,17] This precipitates a salt form which, after redissolving, was acidified to precipitate analytically pure H1 in 80 % yield.…”