Theoretical Studies on Metal−Metal Interaction, Excited States, and Spectroscopic Properties of Binuclear Au−Au, Au−Rh, and Rh−Rh Complexes with Diphosphine Ligands: Buildup of Complexity from Monomers to Dimers

Abstract

To understand their photocatalytic activity and application in luminescent materials, a series of gold and rhodium phosphine complexes (mononuclear [Au(I)(PH(3))(2)](+) (1) and [Rh(I)(CNH)(2)(PH(3))(2)](+) (2); homobinuclear [Au(I)(2)(PH(2)CH(2)PH(2))(2)](2+) (3) and [Rh(I)(2)(CNH)(4)(PH(2)CH(2)PH(2))(2)](2+) (4); heterobinuclear [Au(I)Rh(I)(CNH)(2)(PH(2)CH(2)PH(2))(2)](2+) (5), [Au(I)Rh(I)(CNH)(2)(PH(2)NHPH(2))(2)Cl(2)] (6), and [Au(I)Rh(I)(CNH)(2)(PH(2)NHPH(2))(2)](2+) (7); and oxidized derivatives [Au(II)Rh(II)(CNH)(2)(PH(2)CH(2)PH(2))(2)](4+) (8), [Au(II)Rh(II)(CNH)(2)(PH(2)NHPH(2))(2)Cl(3)](+) (9), and [Au(II)Rh(II)(CNH)(2)(PH(2)NHPH(2))(2)](4+) (10)) were investigated using ab initio methods and density functional theory. With the use of the MP2 method, the M-M' distances in 3-7 were estimated to be in the range of 2.76-3.02 A, implying the existence of weak metal-metal interaction. This is further evident in the stretching frequencies and bond orders of M-M'. The two-electron oxidation from 5-7 to their respective partners 8-10 was shown to mainly occur in the gold-rhodium centers. Experimental absorption spectra were well reproduced by our time-dependent density functional theory calculations. The metal-metal interaction results in a large shift of d(z(2)) --> p(z) transition absorptions in binuclear complexes relative to mononuclear analogues and concomitantly produces a low-lying excited state that is responsible for increasing visible-light photocatalytic activities. Upon excitation, the metal-centered transition and the metal-to-metal charge transfer strengthen the metal-metal interaction in triplet excited states for 3-6, while the promotion of electrons into the sigma*(d(z(2))) orbital weakens the interaction in 9.

Two Metals Are Better Than One in the Gold Catalyzed Oxidative Heteroarylation of Alkenes

“…We also considered a possible bimetallic oxidation (2-electron 2-center) pathway characterized by a concerted oxidation of a weakly bound Au(I) dimer. 10 Au(I) –Au(I) interactions or “aurophilic bonding”, 11 especially in complexes with bidentate ligands 10,12 (e.g. dppm) may favor the bimetallic oxidation pathway (Scheme 2c).…”

Structures and spectroscopic properties of ruthenium phenanthroline solar-cell sensitizers: A computational study

“…doi:10.1016/j.cplett.2011.03.016 density functional theory (TD-DFT) [15][16][17] with the same B3LYP functional was performed to calculate absorption spectra of complexes. Considering the influence of solvent on electronic spectra as indicated in our previous studies [18][19][20], we employed the conductor-like polarizable continuum model (CPCM) [21] to account for the solvent effect of methanol. We carried out the Hay and Wadt [22,23] effective core potentials (ECPs) calculations for Ru and S. The LANL2DZ basis sets associated with the ECPs were employed.…”

Theoretical Study of Metallophilic Interactions and Excited States of Heterobimetallic d10−d8 Complexes with Bridging Ligands: The Tuning of Electronic Spectroscopy

“…In the calculations, we used hydrogen atoms to represent the R (R = Me, Et, and Ph) groups that bond to the real ligands (PR 2 CH 2 PR 2 , CH 2 PR 2 CH 2 , and CCR). This kind of simplification has been successfully applied in previous works. − ,− , Therefore, we began by exploring the reference complex [Au I M′(R 1 ) 2 (R 2 ) 2 ] (M′ = Pt II , R 1 = CN − , R 2 = PH 2 CH 2 PH 2 ; 1 ), which has been studied experimentally by structural and spectroscopic characterization. − To study the effects of heterometal centers, the coordination environments of the d 8 metal, and the bridging ligands on the metal−metal interaction, excited state, and electronic spectroscopy, we designed complexes with different heterometals (M′ = Pt II , Au III ), bonding groups (R 1 = CN − , CCH − ), and bridging ligands (R 2 = PH 2 CH 2 PH 2 , CH 2 PH 2 CH 2 − ) relative to those of 1 . Scheme includes [Au I Pt III (CN) 2 (PH 2 CH 2 PH 2 ) 2 ] 2+ ( 1 ), [Au I Au III (CN) 2 (PH 2 CH 2 PH 2 ) 2 ] 2+ ( 2 ), [Au I Pt II (CCH) 2 (PH 2 CH 2 PH 2 ) 2 ] + ( 3 ), [Au I Pt II (CN) 2 (CH 2 PH 2 CH 2 ) 2 ] − ( 4 ), [Au I Au III (CCH) 2 (PH 2 CH 2 PH 2 ) 2 ] 2+ ( 5 ), [Au I Pt II (CCH) 2 (CH 2 PH 2 CH 2 ) 2 ] − ( 6 ), [Au I Au III (CN) 2 (CH 2 PH 2 CH 2 ) 2 ] ( 7 ), and [Au I Au III (CCH) 2 (CH 2 PH 2 CH 2 ) 2 ] ( 8 ).…”

“…A number of d 8 complexes, such as Au(III), Pt(II), Pd(II), Ni(II), and Rh(I), also exhibit weak metal−metal interactions and intensive luminescence. − So far, the synthesis of complexes has been devoted to combining a d 8 metal center with a d 10 center through a heterometallic interaction. − The heterobimetallic Au(I)−metal complexes can take advantage of the maximum relativistic effects of gold to increase the metallophilicity. − ,− Many reported complexes use bridging ligands to pull two metals into close proximity. − These complexes not only have an undoubted theoretical interest but can comprise a new class of photoluminescent material as well. ,,− …”