Probing Ruthenium−Acetylide Bonding Interactions:  Synthesis, Electrochemistry, and Spectroscopic Studies of Acetylide−Ruthenium Complexes Supported by Tetradentate Macrocyclic Amine and Diphosphine Ligands

Abstract

The synthesis and spectroscopic properties of trans-[RuL4(C[triple bond]CAr)2] (L4 = two 1,2-bis(dimethylphosphino)ethane, (dmpe)2; 1,5,9,13-tetramethyl-1,5,9,13-tetraazacyclohexadecane, 16-TMC; 1,12-dimethyl-3,4:9,10-dibenzo-1,12-diaza-5,8-dioxacyclopentadecane, N2O2) are described. Investigations into the effects of varying the [RuL4] core, acetylide ligands, and acetylide chain length for the [(-)C[triple bond]C(C6H4C[triple bond]C)(n-1)Ph] and [(-)C[triple bond]C(C6H4)(n-1)Ph] (n = 1-3) series upon the electronic and electrochemical characteristics of trans-[RuL4(C[triple bond]CAr)2](0/+) are presented. DFT and TD-DFT calculations have been performed on trans-[Ru(L')4(C[triple bond]CAr)2](0/+) (L' = PH3 and NH3) to examine the metal-acetylide pi-interaction and the nature of the associated electronic transition(s). It was observed that (1) the relationship between the transition energy and 1/n for trans-[Ru(dmpe)2{C[triple bond]C(C6H4C[triple bond]C)(n-1)Ph}2] (n = 1-3) is linear, and (2) the sum of the d(pi)(Ru(II)) --> pi*(C[triple bond]CAr) MLCT energy for trans-[Ru(16-TMC or N2O2)(C[triple bond]CAr)2] and the pi(C[triple bond]CAr) --> d(pi)(Ru(III)) LMCT energy for trans-[Ru(16-TMC or N2O2)(C[triple bond]CAr)2]+ corresponds to the intraligand pi pi* absorption energy for trans-[Ru(16-TMC or N2O2)(C[triple bond]CAr)2]. The crystal structure of trans-[Ru(dmpe)2{C[triple bond]C(C6H4C[triple bond]C)2Ph}2] shows that the two edges of the molecule are separated by 41.7 A. The electrochemical and spectroscopic properties of these complexes can be systematically tuned by modifying L4 and Ar to give E(1/2) values for oxidation of trans-[RuL4(C[triple bond]CAr)2] that span over 870 mV and lambda(max) values of trans-[RuL4(C[triple bond]CAr)2] that range from 19,230 to 31,750 cm(-1). The overall experimental findings suggest that the pi-back-bonding interaction in trans-[RuL4(C[triple bond]CAr)2] is weak and the [RuL4] moiety in these molecules may be considered to be playing a "dopant" role in a linear rigid pi-conjugated rod.

Ligand‐to‐Ligand Charge‐Transfer Transitions of Platinum(II) Complexes with Arylacetylide Ligands with Different Chain Lengths: Spectroscopic Characterization, Effect of Molecular Conformations, and Density Functional Theory Calculations

“…[26] All calculations were performed using the Gaussian 03 program package. [27] RR spectra were acquired by using the apparatus and methods previously detailed in references [8] and [30].…”

Synthesis and charge transfer characteristics of a ruthenium–acetylide complex

“…More recently, their charge transfer behaviour was investigated by various methods, including mechanically controllable break junction (MCBJ), where this class of complexes demonstrated high conductivity 1,2 and spectro-electrochemical analysis, in which their redox responsiveness and different charge transfer modes such as metal-toligand charge-transfer (MLCT), ligand-to-metal charge-transfer (LMCT) and even inter valence charge transfer (IVCT) were studied. [3][4][5] Yet while the through-bond charge transfer behaviours were investigated by the above-mentioned methods, their through-space (or inter-molecular) charge transfer ability still remains ambiguous despite of its importance for organic electronic applications. Furthermore, unlike other Ru-compounds, which have been used as dopants for (organic) semiconductors, the doping ability of ruthenium-acetylide complexes is still unclear.…”

Syntheses and molecular structures of trans-bis(alkynyl) tetrakis-triethylphosphite ruthenium complexes

“…The chemistry of trans-bis(alkynyl) complexes of ruthenium has been extensively developed over the past decades, and whilst the vast majority are supported by ancillary phosphine ligands, [1][2][3][4] examples with other supporting ligand sets, including, for example, mixed phosphine-carbonyl [5,6] or N-heterocyclic carbenecarbonyl [7] ligand sets, macrocyclic amines and dioxodiazamacrocyles [8,9] are also known. In addition to finding extensive application as building blocks and donors for the construction of NLO active materials, [10,11] including chemically and redoxswitchable examples, [12,13] donor molecules within solar cells [14][15][16] and applications as sensors, [17] trans-[Ru(C≡CR) 2 (dppe) 2 ] [dppe = 1,2bis(diphenylphosphino)ethane] complexes systems commonly feature in designs of metal-containing molecular wires.…”