Terence Kwok-Ming Lee

An unprecedented luminescent polynuclear gold(I) μ3-sulfido cluster with a thiacrown-like architecture

An unprecedented Au(18) thiacrown directed by Au(I)···Au(I) interactions and supported by tridentate phosphine (dpepp) and μ(3)-sulfido ligands that highly resembles the 18-membered thiacrown ether [18]aneS(6) in appearance has been synthesized. The sulfides of the Au(3)(μ(3)-S) units in the central cavity point toward each other and are located on the same plane, allowing them to bind the soft Ag(+) ion with immediate and pronounced spectroscopic changes. Reversible binding and spectroscopic changes can be readily achieved upon addition of CH(3)CN without disruption of the Au(18) macrocycle.

Unprecedented near-infrared (NIR) emission in diplatinum(III) (d7-d7) complexes at room temperature.

The synthesis and single-crystal X-ray structures of the first family of efficient NIR emitters with tunable emission energy based on dihalodiplatinum(III) (5d(7)-5d(7)) complexes of general formulae [Pt(2)(mu-C(6)H(3)-5-R-2-AsPh(2))(4)X(2)] (R = Me or CHMe(2); X = Cl, Br or I), together with that of their diplatinum(II) (5d(8)-5d(8)) precursors ([Pt(2)(mu-C(6)H(3)-5-R-2-AsPh(2))(4)]) and cyano counterparts (X = CN), are reported. The diplatinum(II) complexes with isopropyl groups are isolated initially as a mixture of two species, one being a half-lantern structure containing two bridging and two chelate C(6)H(3)-5-CHMe(2)-2-AsPh(2) ligands (1b) that exists in two crystalline modifications [d(Pt...Pt) = 3.4298(2) A and 4.3843(2) A]; the other is a full-lantern or paddle-wheel structure having four bridging C(6)H(3)-5-CHMe(2)-2-AsPh(2) ligands (2b) [d(Pt...Pt) = 2.94795(12) A]. Complete conversion of the isomers into 2b occurs in hot toluene. The Pt-Pt bond distances in the diplatinum(III) complexes are less than that in 2b and increase in the order X = Cl (3b) [2.6896(2) A] < Br (4b) [2.7526(3) A] < I (5b) [2.7927(7) A] approximately CN (6b) [2.7823(2), 2.7924(2) A for two independent molecules]. Comparison with the corresponding data for our previously reported series of complexes 3a-6a (R = Me) indicates that the Pt-Pt bond lengths obtained from single-crystal X-ray analysis are influenced both by the axial ligand and by intermolecular lattice effects. Like [Pt(2)(mu-pop)(4)](4-) [pop = pyrophosphite, (P(2)O(5)H(2))(2-)], the diplatinum(II) complexes [Pt(2)(mu-C(6)H(3)-5-R-2-AsPh(2))(4)] [R = Me (2a), CHMe(2) (2b)] display intense green phosphorescence, both as solids and in solution, and at room temperature and 77 K, with the emission maxima in the range 501-532 nm. In contrast to the reported dihalodiplatinum(III) complexes [Pt(2)(mu-pop)(4)X(2)](4-) that exhibit red luminescence only at 77 K in a glass or as a solid, complexes 3a-6a and 3b-6b are phosphorescent in the visible to near-infrared region at both room and low temperatures. The electronic spectra and photoemissive behavior are discussed on the basis of time-dependent density functional theory (TDDFT) calculations at the B3YLP level. The photoemissive states for the halide analogues 3a,b-5a,b involve a moderate to extensive mixing of XMMCT character and MC [d sigma-d sigma*] character, whereas the cyano complexes 6a and 6b are thought to involve relatively less mixing of the XMMCT character into the MC [d sigma-d sigma*] state.

Self-assembly of a neutral luminescent Au12 cluster with D2 symmetry

The preparation and characterization of luminescent neutral Au(12) shuttle-like complexes is reported which shows a cyclic framework consisting of twelve gold(i) ions arranged in a closed ring via non-covalent Au(i)Au(i) interactions to give a chiral D(2) symmetrical structure.

Synthesis, characterization, and luminescence studies of discrete polynuclear gold(I) sulfido and selenido complexes with intramolecular aurophilic contacts.

The synthesis, characterization, and photophysical and photochemical properties of a family of high-nuclearity gold(I) chalcogenides, specifically, the gold(I) sulfido and selenido complexes containing different bridging diphosphine ligands with nuclearities of ten ([Au10{μ-Ph2PN(R)PPh2}4(μ3-E)4](2+)) and six ([Au6{μ-Ph2PN(R)PPh2}3(μ3-E)2](2+)), are reported. The X-ray crystal structures of the complex cations of Au10 and Au6 are found to be propeller-like structures and distorted cubane structures, respectively, with the presence of short intramolecular gold···gold distances. The complexes show intense green and/or orange phosphorescence upon photoexcitation in the solid state and in solution at ambient and low temperature. The emission properties are found to be strongly dependent on the nuclearities and the chalcogenido ligands, but are rather insensitive to the substituents on the bis(diphenylphosphino)amines. The emissions are tentatively assigned to originate from the excited states derived from the phosphine-centered intraligand (IL) transition or metal-centered (ds/dp) mixed with ligand-to-metal-metal charge transfer (LMMCT) (E→Au) transition. The photochemical properties of the complexes were also studied by transient absorption spectroscopy.

Luminescence Color Switching of Supramolecular Assemblies of Discrete Molecular Decanuclear Gold(I) Sulfido Complexes

Significance Polynuclear gold(I) complexes have attracted enormous attention over the past decades owing to their intriguing luminescence behavior and their interesting structural and bonding properties, especially with regard to their propensity to form noncovalent short gold–gold contacts. Most works in polynuclear gold(I) clusters involve structural studies in the solid state, with less attention focused on supramolecular assembly in solution. Herein, discrete decanuclear gold(I) μ3-sulfido complexes with long alkyl chains are found to form supramolecular assemblies with different luminescence and morphologies that are tunable by solvent modulation. This has demonstrated the importance of the control and manipulation of intercluster assembly in influencing the photophysical properties and morphologies of the clusters. Such findings have not been previously reported in discrete molecular gold(I) systems. A series of discrete decanuclear gold(I) μ3-sulfido complexes with alkyl chains of various lengths on the aminodiphosphine ligands, [Au10{Ph2PN(CnH2n+1)PPh2}4(μ3-S)4](ClO4)2, has been synthesized and characterized. These complexes have been shown to form supramolecular nanoaggregate assemblies upon solvent modulation. The photoluminescence (PL) colors of the nanoaggregates can be switched from green to yellow to red by varying the solvent systems from which they are formed. The PL color variation was investigated and correlated with the nanostructured morphological transformation from the spherical shape to the cube as observed by transmission electron microscopy and scanning electron microscopy. Such variations in PL colors have not been observed in their analogous complexes with short alkyl chains, suggesting that the long alkyl chains would play a key role in governing the supramolecular nanoaggregate assembly and the emission properties of the decanuclear gold(I) sulfido complexes. The long hydrophobic alkyl chains are believed to induce the formation of supramolecular nanoaggregate assemblies with different morphologies and packing densities under different solvent systems, leading to a change in the extent of Au(I)–Au(I) interactions, rigidity, and emission properties.

Synthesis and structures of cyclic gold complexes containing diphosphine ligands and luminescent properties of the high nuclearity species

A mixture of cyclic gold(I) complexes [Au(2)(μ-cis-dppen)(2)]X(2) (X = OTf 1, PF(6)3) and [Au(cis-dppen)(2)]X (X = OTf 2, PF(6)4) is obtained from the reaction of [Au(tht)(2)]X (tht = tetrahydrothiophene) with one equivalent of cis-dppen [dppen = 1,2-bis(diphenylphosphino)ethylene]. The analogous reaction with trans-dppen or dppa [dppa = bis(diphenylphosphino)acetylene] affords the cyclic trinuclear [Au(3)(μ-trans-dppen)(3)]X(3) (X = OTf 11, PF(6)12) and tetranuclear [Au(4)(μ-dppa)(4)]X(4) (X = OTf 13, PF(6)14, ClO(4)15) gold complexes, respectively. Recrystallization of 15 from CH(2)Cl(2)/MeOH yielded a crystal of the octanuclear gold cluster [Au(8)Cl(2)(μ-dppa)(4)](ClO(4))(2)16. Attempts to prepare dicationic binuclear gold(II) species from the reaction of a mixture of 3 and 4 with halogens gave a mixture of products, the components of which confirmed to be acyclic binuclear gold(I) [Au(2)X(2)(cis-dppen)] (X = I 5, Br 7) and cyclic mononuclear gold(III) [AuX(2)(cis-dppen)]PF(6) (X = I 6, Br 8) complexes. Complexes 11-14 reveal weak emission in butyronitrile glass at 77 K, but they are non-emissive at room temperature. Ab initio modelling was performed to determine the charge state of the gold atoms involved. Extensive structural comparisons were made to experimental data to benchmark these calculations and rationalize the conformations.

Thermodynamic-Driven Self-Assembly: Heterochiral Self-Sorting and Structural Reconfiguration in Gold(I)–Sulfido Cluster System

By employing chiral precursors, a new class of chiral gold(I)-sulfido clusters with unique structures has been constructed. Interestingly, pure enantiomers of the precursors are found to self-assemble into chiral hexa- and decanuclear clusters sequentially, while a racemic mixture of them has resulted in heterochiral self-sorting of an achiral meso decanuclear cluster. Chirality has determined not only the symmetry and structures but also the photophysical behaviors of these clusters. The racemic mixture of decanuclear clusters undergoes rearrangement and heterochiral self-sorting to give a meso decanuclear cluster. The thermodynamic-driven heterochiral self-sorting of gold(I) clusters provides a means to develop controlled self-assembly that may be of relevance to the understanding of chirality in nature.