Conformation Changes and Luminescent Properties of Au-Ln (Ln = Nd, Eu, Er, Yb) Arrays with 5-Ethynyl-2,2′-Bipyridine

Abstract

Reaction of polymeric gold(I) acetylide species (bpyC[triple bond]CAu)n (bpyC[triple bond]CH = 5-ethynyl-2,2'-bipyridine) with diphosphine ligands Ph2P(CH2)nPPh2 (n = 2-6) or 1,1'-bis(diphenylphosphino)-ferrocene (dppf) in dichloromethane induces isolation of binuclear gold(I) complexes (bpyC[triple bond]CAu)2{mu-Ph2P(CH2)nPPh2} or (bpyC[triple bond]CAu)2(mu-dppf). Complexation of Ln(hfac)3 (hfac = hexafluoroacetylacetonate, Ln = Nd, Eu, Er, Yb) subunits to the binuclear gold(I) complexes through 2,2'-bipyridyl chelation gives the corresponding Au4Ln4 or Au2Ln2 heteropolynuclear complexes. Noticeably, upon formation of the Au4Ln4 arrays by complexation of (bpyC[triple bond]CAu)2(mu-Ph2P(CH2)4PPh2) (3) with Ln(hfac)3 units, trans-conformation in 3 transforms dramatically to the cis-arranged form due to the strong driving force from ligand-unsupported Au-Au contacts between two Au2Ln2 subunits. In contrast, cis-conformation in (bpyC[triple bond]CAu)2(mu-dppf) (6) stabilized by Au-Au interactions is reversed to the trans-oriented form upon formation of Au2Ln2 arrays by introducing Ln(hfac)3 units through 2,2-bipyridyl chelation. The binuclear gold(I) complexes show bright blue luminescence featured by ligand-centered pi --> pi* (C[triple bond]Cbpy) states together with low-energy emission at 500-540 nm, associated with 3(pi-->pi*) excited states, mixed probably with some characteristic from (Au-Au) --> (C[triple bond]Cbpy) 3MMLCT transition. For Au4Ln4 or Au2Ln2 complexes, sensitized lanthanide luminescence is achieved by energy transfer from Au-acetylide chromophores with lifetimes in the sub-millisecond range for EuIII complexes, whereas in the microsecond range for near-infrared emitting NdIII, ErIII, and YbIII species.

Polypyridyl-functionalizated alkynyl gold(i) metallaligands supported by tri- and tetradentate phosphanes

“…In fact, some research groups have recently described the synthesis of alkynyl gold(I) complexes with terminal 2,2′-bipyridine [41][42][43][44][45][46] or 2,2′:6′,2″-terpyridine units. 41,[47][48][49][50] Interestingly, however, in spite of the stability of these metallaligands, a limited number of reports on the supramolecular coordination chemistry of these species can be found in the literature.…”

“…Some years ago, Chen and co-workers described the isolation of tetrametallic Au 2 Ln 2 (Ln = lanthanide) arrays formed by the establishment of aurophilic interactions. 42 Very recently, Vicente and co-workers reported the obtention of appealing supramolecular architectures like triple-stranded helicates, 51,52 helical dimers, 53 rigid-rod complexes and coordination oligomers. 54 Noteworthily, all the reported alkynyl gold(I) compounds with pendant polypyridyl moieties mentioned above are supported by mono or diphosphanes as auxiliary ligands, and consequently are able to act as mono or ditopic metallaligands.…”

Structural and Photophysical Properties of (Phosphane)gold(I)‐Decorated 4,4′‐Diethynyl‐2,2′‐bipyridine Ligands

“…[3,[9][10][11] By combining phosphine and alkyne metal-binding domains at a gold(I) centre, one gains significant scope for the design of macromolecules: [12] rigid-rod P-Au-C≡C-domains and a wide range of readily accessible mono-, bi-and polydentate phosphine ligands containing sp 3 hybridized P atoms combine with a tendency for gold atoms to aggregate (so-called 'aurophilicity'). [13][14][15]16] Of the 215 compounds in the CSD (CSD v 5.3 with May 2009 updates, Conquest v. 1.11) [17] possessing R 3 PAuC≡C units, only 19 [9,[18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] exhibit intermolecular aurophilic interactions resulting in onedimensional Au...Au bonded polymers. Of particular relevance to our work is the trigold derivative ( n Bu 3 PAuC≡CCH 2 OCH 2 ) 3 CCH 2 Otpy (tpy = 2,2';6',2"-terpyridine) which forms one-dimensional chains with an oriented assembly in the solid state in which all the tpy units point in the same direction.…”

The Coordination and Supramolecular Chemistry of Gold Metalloligands

“…2018,24,[32][33][34][35][36][37][38][39][40][41][42][43][44][45][46] www.chemeurj.org to six different metal centers, such as 57,t hrough severals uccessive metalloligand-to-metal coordination steps. [53] Alkynyl-gold metalloligands containing two bipyridyl units (58)w ere reported by the groups of Chen [54] andu s ( Figure 15). [48a, 55] Variation of the bridging ligand allows the easy modulation of the length and degree of flexibility of the metalloligand as wella st he synthesis of chiral metalloligands from chiral diphosphines.…”

“…This was attributed to energy transfer from the excited Au-alkynyl luminophore to the [Ln(hfac) 3 (bpy)] unit. [54] We have reported that three metalloligands of the type 58 and two Fe 2 + ,C o 2 + ,o rZ n 2 + ions self-assemble to form triplestranded helicates 60 (Scheme 5). The X-ray structures of two of these M 2 Au 6 complexes showed that the helicate strands are folded, giving rise to at riple-looped structure, which is stabilized by Au···Au,C H···p,a nd p···p interactions (Scheme 5).…”