Rational Assembly of Metallophilic Gold(I)–Lead(II) and Gold(I)–Gold(I) Puzzle Pieces

Heteronuclear Gold(I)-Copper(I) Complexes with Thia- and Mixed Thia-Aza Macrocyclic Ligands: Synthesis, Structures and Optical Properties

The reactivity of the heterometallic polynuclear complexes [{Au(R)2 }2 Cu2 (MeCN)2 ]n (R=C6 F5 , C6 Cl5 ) with the thioether crowns 1,4,7-trithiacyclononane (L1, [12]aneS3 ), 1,4,8,11-tetrathiacyclododecane (L2, [14]aneS4 ), 1,4,7,10,13,16,19,22-octathiacyclotetracosane (L3, [24]aneS8 ), and the quinoline functionalized pendant arm derivatives of the 12-membered mixed-donor macrocycles 1-aza-,4,7,10-trithiacyclododecane ([12]aneNS3 ) and 1,7-diaza-4,10-dithiacyclododecane ([12]aneN2 S2 ), L4 and L5, respectively, was investigated in THF solution. While with L4 and L5 only ionic compounds of general formulation [Cu(L)][Au(R)2 ] were isolated and structurally characterized (none of them featuring Au⋅⋅⋅Cu interactions), with L1-L3, beside similar ionic compounds, some heteronuclear complexes of general formulation [{Au(R)2 }{Cu(L)}] and featuring Au⋅⋅⋅Cu interactions were also obtained. All of them display rather unusual non-classical C-H⋅⋅⋅Au hydrogen interactions. The complexes display in the solid state different optical properties related to their structures, which have been studied experimentally and theoretically via TD-DFT calculations. In particular, all compounds of the type [{Au(R)2 }{Cu(L)}] featuring Au⋅⋅⋅Cu metallophilic interactions display luminescence in the solid state both at room temperature (RT) and at 77 K. On the contrary, ionic compounds of general formulation [Cu(L)][Au(R)2 ], except [Cu(L4)][Au(C6 F5 )2 ], are not luminescent.

Vapochromic behaviour of a gold(I)-lead(II) complex as a VOC sensor

The reaction among [Au2Ag2(C6F5)4(OEt2)2]n, PbCl2 and terpyridine leads to the polymeric complex [{Au(C6F5)2}2{Pb(terpy)}]n (1). Its crystal structure reveals potential voids close to the lead centres large enough to hold different molecules. The availability of these free sites allows complex 1 to act as a VOC sensor. Thus, when 1 is exposed to different solvent vapours such as acetonitrile, toluene or THF, variations in its solid appearance and its photophysical properties are observed as a consequence of the formation of the new polymorphs [{Au(C6F5)2}2{Pb(terpy)(CH3CN)2}]n (2), [{Au(C6F5)2}2{Pb(terpy)}]n·Tol (3) and [{Au(C6F5)2}2{Pb(terpy)(THF)}]n·THF (4). Each polymorph displays a different emission energy depending on its structure and the presence of metallophilic interactions. In addition, the reversible solvent molecule exchange allows the tuning of the luminescence emissions in the greenish yellow-red range. DFT and TD-DFT calculations were performed to explain the origin of the luminescence of all these complexes.

Mixed-Valence Tetrametallic Iridium Chains

Neutral [X-{Ir2 }-{Ir2 }-X] (X=Cl, Br, SCN, I) and dicationic [L-{Ir2 }-{Ir2 }-L]2+ (L=MeCN, Me2 CO) tetrametallic iridium chains made by connecting two dinuclear {Ir2 } units ({Ir2 }=[Ir2 (μ-OPy)2 (CO)4 ], OPy=2-pyridonate) by an iridium-iridium bond are described. The complexes exhibit fractional averaged oxidation states of +1.5 and electronic delocalization along the metallic chain. While the axial ligands do not significantly affect the metal-metal bond lengths, the metallic chain has a significant impact on the iridium-L/X bond distances. The complexes show free rotation around the unsupported iridium-iridium bond in solution, with a low-energy transition state for the chloride chain. The absorption spectra of these complexes show characteristic bands at 438-504 nm, which can be fine-tuned by varying the terminal capping ligands.

Switching On/Off of a Solvent Coordination in a Au(I)-Pb(II) Complex: High Pressure and Temperature as External Stimuli

The benzonitrile solvate {[{Au(C6F5)2}2{Pb(terpy)}]·NCPh}n (1) (terpy = 2,2':6',2″-terpyridine) displays reversible reorientation and coordination of the benzonitrile molecule to lead upon external stimuli. High-pressure X-ray diffraction studies between 0 and 2.1 GPa reveal a 100% of conversion without loss of symmetry, which is totally reversible upon decompression. By variable-temperature X-ray diffraction studies between 100 and 285 K, a partial coordination is achieved.

Computational prediction of Au(I)-Pb(II) bonding in coordination complexes and study of the factors affecting the formation of Au(I)-E(II) (E = Ge, Sn, Pb) covalent bonds

We have studied computationally the Au-M (M = Ge, Sn, Pb) bonding trends in a series of model systems [(PH3)3Au-(MCl3)] (M = Ge (4), Sn (5), Pb (6)). For this, we have fully optimized the model systems at the MP2 level of theory, computing the Au-M bonding energy at the equilibrium distances applying the counterpoise (cp) correction to the basis-set superposition error (BSSE) and performing a natural energy decomposition analysis (NEDA). Furthermore, a topological analysis of the electron density using QTAIM, ELF and DORI tools was performed. In order to provide further insights on the possibility of predicting the existence of Au(i)-Pb(ii) donor bonds, Density Functional Theory calculations using the pbe functional and including dispersion corrections (DFT-D3/pbe) were performed on three model systems, [(PR3)3Au-(PbCl3)] (R = CH3 (7), H (8), CF3 (9)). This study also includes the corresponding NEDA calculations and the topological analysis of the electron density, which provides information about the Au-Pb bond, but also about the supporting weak ligand-ligand interactions. Overall, the study provides information about the factors affecting the formation of stabilizing Au(i)-Pb(ii) covalent bonds.

Luminescent gold-thallium derivatives with a pyridine-containing 12-membered aza-thioether macrocycle

The coordination modes of the ligand 2,5,8-trithia[9](2,6)pyridinophane (L) to thallium(i), gold(iii) and gold(i) have been studied. Thallium(i) is coordinated by the macrocyclic ligand in [Tl(L)](PF6) (1) through all the sulfur and nitrogen atoms, in a distorted square-pyramidal geometry with the thallium(i) ion in the apical position and with the presence of an inert lone pair. Gold(iii) is bonded by the ligand only through the nitrogen of the pyridine group in [AuCl3(L)] (2), whereas two AuI-C6F5 fragments coordinate the sulfur atoms next to the pyridine moiety of the ligand in [{Au(C6F5)}2(μ-L)] (3), which form a linear polymer through intermolecular aurophilic contacts. The heterometallic TlI/AuI complex {[Au(C6F5)2Tl]2(L)}n (4) features a polymeric structural nature with a metallic pseudo-rhombic Au2Tl2 core, which repeats itself forming a zig-zag polymer. In each Au2Tl2 unit only one thallium atom is bonded by the NS3 donor set of the macrocyclic ligand and also forms two unsupported Au-Tl bonds with two [Au(C6F5)2]- units in an overall pseudo-octahedral geometry. The other thallium atom similarly bridges the same [Au(C6F5)2]- units and links a neighbouring Au2Tl2 moiety, thus exhibiting a distorted trigonal planar geometry being bonded only to three gold atoms with unsupported Au-Tl interactions. This complex displays an interesting thermochromic behaviour showing emissions mainly resulting from MM'CT transitions at room temperature. At 77 K a dual emission appears, probably arising from the two different thallium environments. DFT calculations have been carried out in the attempt to investigate the origin of the emissions of complex 4.