David Pascual

Amalgamating at the molecular level. A study of the strong closed-shell Au(I)···Hg(II) interaction.

Complex {[Hg(C(6)F(5))(2)][Au(C(6)F(5))(PMe(3))](2)}(n)2 displays unsupported Au(I)···Hg(II) and Au(I)···Au(I) interactions. Its crystal structure displays a polymeric -(Au-Hg-Au-Au-Hg-Au)(n)- disposition. Ab initio calculations show very strong Au(I)···Hg(II) and Au(I)···Au(I) closed-shell interactions of -73.3 kJ mol(-1) and -57.0 kJ mol(-1), respectively, which have a dispersive (van der Waals) nature and are strengthened by large relativistic effects (>20%).

Influence of the electronic characteristics of N-donor ligands in the excited state of heteronuclear gold(I)-copper(I) systems.

By reaction of the heterometallic gold-silver complexes [{AuAg(C(6)F(5))(2)(N≡C-Me)}(2)](n) or [{AuAg(C(6)Cl(5))(2)(N≡C-Me)}(2)](n) and CuCl in the presence of pyrimidine and different nitrile ligands (acetonitrile, benzonitrile, and cinnamonitrile), the heteronuclear complexes {[Au(C(6)X(5))(2)][Cu(L)(μ(2)-C(4)H(4)N(2))]}(n) (X = F and L = N≡C-Me (1), L = N≡C-Ph (2) or N≡C-CH═CH-Ph (3); X = Cl and L = N≡C-Me (4), N≡C-Ph (5), N≡C-CH═CH-Ph (6)) have been prepared. The crystal structures of complexes {[Au(C(6)X(5))(2)][Cu(L)(μ(2)-C(4)H(4)N(2))]}(n) (X = F; L = N≡C-CH═CH-Ph (3), X = Cl; L = N≡C-Ph (5)) have been determined by X-ray diffraction studies. The crystal structures of both complexes consists of polymeric chains formed by the repetition of [Au(C(6)X(5))(2)][Cu(L)(μ(2)-C(4)H(4)N(2))] units through copper-pyrimidine bonds. Complexes 1, 2, 4, and 5 are brightly luminescent in the solid state at room temperature and at 77 K with lifetimes in the microseconds range. These compounds are also luminescent in solution, displaying different photophysical behaviors depending on the donor characteristics of the solvents used. The distortion in the excited state allows an associative attack by donor solvents quenching one of the emitting excited states. DFT optimizations of the ground (S(0)) and lowest triplet excited state (T(1)) display the structure distortion of the complexes upon electronic excitation. The molecular orbitals involved in the electronic transitions responsible for the phosphorescence in the case of the complexes 1, 2, 4, and 5 are related to metal (gold-copper) to ligand (pyrimidine) charge transfer transitions, while in the case of the nonluminescent complexes 3 and 6, the nonradiative electronic transition arises from metal (gold-copper) to ligand (cinnamonitrile) charge transfer transitions.

Experimental and Theoretical Comparison of the Metallophilicity between d10–d10 AuI–HgII and d8–d10 AuIII–HgII Interactions

The heteronuclear Au(I)/Hg(II) complexes [Hg{AuR(μ-2-C6H4PPh2)}2] [R = C6F5 (1), C6Cl2F3 (2)] were prepared by reacting [Hg(2-C6H4PPh2)2] with [AuR(tht)] (1:2) and further transformed into the Au(III)/Hg(II) species [Hg{Au(C6F5)Cl2(μ-2-C6H4PPh2)}2] [R = C6F5 (3), C6Cl2F3 (4)] by the addition of 2 equiv of PhI·Cl2. The crystal structures of 1-3 display Au···Hg(II) interactions, which in the case of 3 is the first Au(III)···Hg contact described to date. Theoretical calculations on model systems of the C6F5 derivatives evidence that the attraction between Au(I) or Au(III) and Hg(II) arise from dispersion-type interactions and that both contacts are of the same strength.

Pt–Mg, Pt–Ca, and Pt–Zn Lantern Complexes and Metal-Only Donor–Acceptor Interactions

Pt-based heterobimetallic lantern complexes of the form [PtM(SOCR)4(L)] have been shown previously to form intermolecular metallophilic interactions and engage in antiferromagnetic coupling between lanterns having M atoms with open shell configurations. In order to understand better the influence of the carboxylate bridge and terminal ligand on the electronic structure, as well as the metal-metal interactions within each lantern unit, a series of diamagnetic lantern complexes, [PtMg(SAc)4(OH2)] (1), [PtMg(tba)4(OH2)] (2), [PtCa(tba)4(OH2)] (3), [PtZn(tba)4(OH2)] (4), and a mononuclear control (Ph4P)2[Pt(SAc)4] (5) have been synthesized. Crystallographic data show close Pt-M contacts enforced by the lantern structure in each dinuclear case. 195Pt-NMR spectroscopy of 1-4, (Ph4P)2[Pt(SAc)4] (5), and several previously reported lanterns revealed a strong chemical shift dependence on the identity of the second metal (M), mild influence by the thiocarboxylate ligand (SOCR; R = CH3 (thioacetate, SAc), C6H5 (thiobenzoate, tba)), and modest influence from the terminal ligand (L). Fluorescence spectroscopy has provided evidence for a Pt···Zn metallophilic interaction in [PtZn(SAc)4(OH2)], and computational studies demonstrate significant dative character. In all of 1-4, the short Pt-M distances suggest that metal-only Lewis donor (Pt)-Lewis acceptor (M) interactions could be present. DFT and NBO calculations, however, show that only the Zn examples have appreciable covalent character, whereas the Mg and Ca complexes are much more ionic.

Tailor-Made Luminescent Polymers through Unusual Metallophilic Interaction Arrays Au···Au···Ag···Ag

A novel and efficient strategy for the synthesis of luminescent polymers bearing metallophilic interactions with unprecedented charge sequences has been designed. For this end suitable basic gold units such as [AuR2]-, bearing perhalophenyl derivatives, and dinuclear acid silver terpyridine species, [Ag2(terpy)2](CF3SO3)2, have been chosen. Their combination originates the polymeric derivatives [{AuR2}2Ag2(terpy)2]n (R = C6F5, C6Cl2F3) or [{Au(C6Cl5)2}Ag(terpy)]n. The change of the perhalophenyl group in the gold complex modulates the strength in the metallophilic contacts and, consequently, the polymer arrays and luminescent properties. The X-ray diffraction studies of these derivatives revealed that there are polymers with unusual + + - - + + - - charge sequences for the R = C6F5 and C6Cl2F3 species, whereas the more classical + - + - disposition was found for the bulkiest C6Cl5 derivative. Their luminescent properties also vary depending on the formation of these polymer arrays, and time-dependent density functional theory calculations were performed to determine the origin of the luminescence.

Cooperative Au(I)···Au(I) Interactions and Hydrogen Bonding as Origin of a Luminescent Adeninate Hydrogel Formed by Ultrathin Molecular Nanowires

Two water-soluble [Au(9 N-adeninate)(PR3)] complexes (PR3 = PMe3 (1); PTA (3)) were synthesized by the coordination of the respective cationic [Au(PR3)]+ fragment to the 9 N position of the adeninate anion. Both complexes crystallize as dimers by aurophilic contacts of 3.2081(6) Å in 1 and 3.0942(7) and 3.0969(7) Å in 3, but different packings are observed due to the crystallizing solvent choice and the nature of the ancillary phosphine ligand. At this regard, different supramolecular behavior is observed in water, ranges from the formation of ultrathin nanowires of 5.3 ± 1.9 nm of diameter and up to 1.5 μm in length and leads to a blue-luminescent hydrogel for 1, to the single-crystallization of 3. Parallel computational studies carried out show that aurophilicity and N-H···N or O-H···N hydrogen bonding are comparable in strength, suggesting a competition between all types of weak forces in the final observed macroscopic properties.