Self‐Assembly in Gold(I) Chemistry: A Double‐Stranded Polymer with Interstrand Aurophilic Interactions

Abstract

There has been remarkable progress and interest in the design and synthesis of hybrid organic-inorganic molecular materials, and a key strategy is to design simple building blocks that can be induced to form complex molecular structures by selfassembly.[1] Gold(i) centers are particularly versatile as components of such building blocks based on their tendency for linear coordination, [2, 3] their high reactivity towards ligand substitution, [2] and their ability to form secondary aurophilic bonds that can be used to direct the self-assembly.[2-9] These properties have made it possible to design macrocycles, molecular triangles, catenanes, and polymers with gold(i) centers coordinated to a phosphane and a nitrogen or carbon donor ligand. [2][3][4][5][6][7][8][9][10] The gold-carboxylate linkage is important in self-assembled monolayers on gold colloids [11] and is well known in simple complexes, [2,12] but it has not yet been exploited in molecular materials. Here we show that a simple condensation procedure can lead to the self-assembly of a cyclic dimer or trimer, or of a linear polymer for gold(i) complexes of the three isomers of diphenylphosphanylbenzoic acid, and that the polymer forms a remarkable doublestranded structure through aurophilic attractions. The ligands themselves are already known to give interesting gold compounds [13,14] and bimetallic compounds, [15] and this work further highlights their potential in the field of hybrid organic-inorganic molecular materials. The synthetic strategy was to eliminate HCl from the ortho (1), meta (2), and para (3) isomers of [AuCl(Ph 2 PC 6 H 4 -CO 2 H)], [13,14] to yield the corresponding oligomers or polymers [{Au(Ph 2 PC 6 H 4 CO 2 )} n ], with the expectation that the degree of aggregation would be different for the different isomers. Preliminary experiments with [AuCl(4-Ph 2 P-C 6 H 4 CO 2 H)] (3), which forms a hydrogen-bonded dimer in the solid state (Figure 1), were unsuccessful since the complex was resistant to dehydrochlorination with mild bases and was decomposed by stronger ones. However, success was achieved by a two-step reaction involving abstraction of the chloride ligand from each complex 1-3 using silver(i) trifluoroacetate to form the corresponding gold(i) trifluoroacetate complex, which was not isolated but was treated in situ with a base to eliminate trifluoroacetic acid and give the product, as outlined in Scheme 1. Complex 1 gave a mixture of dimer 4 and trimer 5, while complex 2 gave only a molecular triangle 6, and complex 3 gave an insoluble polymer 7.The soluble complexes 4-6 were characterized in solution by NMR spectroscopy and ESI mass spectrometry. Complex 6 gave a singlet in the 31 P NMR spectrum (in CDCl 3 ) at d = 28.8 ppm and a peak at m/z = 1639 in the ESI-MS (in CH 2 Cl 2 /CH 3 CN, with CsI present to enhance ionization), which corresponds to the [{Au(Ph 2 PC 6 H 4 CO 2 )} 3 ]·Cs + ion, and indicates the presence of the molecular triangle structure only. Complexes 4 and 5 formed an equilibrium mixture in solution. Thus, t...

Ultrathin Gold Nanowires with the Polytetrahedral Structure of Bulk Manganese

“…The first factor is the presence of synergistic effects between the precursor and reducing agents, leading to the emergence of transient chain-like Au (I) complexes that, due to interchain aurophilic interactions and likely excluded volume effects, can self-assemble into nanostructures with a cylindrical shape. 39,43,44 Monovalent Au (I) species inside the nanostructures are reduced to metallic Au (0) species. Atoms at the surface of the nanostructures are in a mixed Au I (5d 10 )/ Au 0 (5d 10 6s 1 ) valence state and likely coordinated by oleylammonium chloride and/or oleylamine ligands.…”

Peptide Coupling between Amino Acids and the Carboxylic Acid of a Functionalized Chlorido-gold(I)-phosphane

“…In the crystal, the complex dimerizes via hydrogen bonds of the carboxylic acid, but no aurophilic interactions are present. 45 Single crystals suitable for X-ray diffraction of the homologue bromido complex, 1b, were obtained from DCM/pentane. Interestingly, it is not isostructural to 1a: It crystallizes in the orthorhombic space group Pbca with two complex molecules and two chloroform molecules in the asymmetric unit (1a: triclinic, P̅ 1).…”