Resonance-Assisted but Antielectrostatic Intramolecular Au···H–O Hydrogen Bonding in Gold(I) Complexes: A Computational Verification

Recent Trends in Group 11 Hydrogen Bonding

Conventional hydrogen bonding (H-bonding) has been extensively studied in organic and biological systems. However, its role in transition metal chemistry, particularly with Group 11 metals (i. e. Cu, Ag, Au) as hydrogen bond acceptors, remains relatively unexplored. Through a combination of experimental techniques, such as Nuclear Magnetic Resonance (NMR), Infrared spectroscopy (IR), X-Ray Diffraction (XRD), and computational calculations, several aspects of H-bonding interactions with Group 11 metals are examined, shedding light on its impact on structural motifs and reactivity. These include bond strengths, geometries, and effects on electronic structures. Understanding the intricacies of hydrogen bonding within transition metal chemistry holds promise for various applications, including catalytic transformations, the construction of molecular assemblies, synthesis of complexes displaying anticancer activities, or luminescence applications (e. g. Thermally Activated Delayed Fluorescence, TADF). This review encompasses the most significant recent advances, challenges, and future prospects in this emerging field.

Selective Phosphate Adsorption Using Topologically Regulated Binary-Defect Metal-Organic Frameworks: Essential Role of Interfacial Electron Mobility

Metal-organic framework (MOF)-modified biochars (BC) have gained recognition as potent adsorbents for phosphate. However, essential insights into the electronic interfacial state of the MOFs remain lacking. In this study, we propose a novel topological transformation strategy to directionally regulate the interfacial electronic states of BC/MOFs composites. The optimized BC/MOFs exhibited an excellent selective phosphate adsorption capacity of 188.68 mg·g-1, coupled with rapid sorption kinetics of 6.81 mg·(g·min0.5)-1 in simulated P-laden wastewater. When challenged with real bioeffluent, such efficacy was still maintained (5 mg·L-1, 25.92 mg·g-1). This superior performance was due to the Fe(III) → Fe(II) transition, promoting electron mobility and leading to the anchoring of Mg(II) to form specific coordination unsaturated sites (Mg-CUS) for phosphate adsorption. Importantly, the simultaneous regulation of binary defects further enhances electron mobility, resulting in the formation of sp3 unequal hybrid orbitals with a stronger internal coupling capability between Mg 3s in Mg-CUS and O 2p in phosphate. Furthermore, the high electron affinity of Mg effectively promotes electron cycling, endowing BC/MOFs with a distinct self-healing capability to facilitate phosphate desorption. The outcomes of this study provide novel perspectives for electronic regulated phosphate adsorption.

Augmenting Metallobasicity to Modulate Gold Hydrogen Bonding

We report the synthesis and characterization of two phosphine gold carbinol species exhibiting intramolecular Au···H-O hydrogen bonding. Increasing the metallobasicity of gold through chloride to phenyl ligand substitution produced an...

A gold(I) 1,2,3-triazolylidene complex featuring the interaction between gold and methine hydrogen

A mesoionic N-heterocyclic carbene-gold(I) complex with a unique Au⋯H-C(methine) intramolecular hydrogen bonding interaction has been investigated in the solid state. The structure of this new neutral gold(I)-carbene was characterized by FT-IR and NMR spectroscopy, TGA, and X-ray diffraction techniques. Density functional theory (DFT) and atoms-in-molecule (AIM) analysis revealed that the gold-hydrogen bonding situation is more favored. Besides, the photophysical properties of the gold(I) complex were also investigated.

The Elusive Au(I)···H-O Hydrogen Bond: Experimental Verification

Our long-standing interest in atypical bonding situations has recently led us to target complexes in which a metallobasic gold(I) center is hydrogen-bonded to a nearby OH functionality. Here, we report on the synthesis and characterization of two neutral gold(I) indazol-3-ylidene complexes bearing a carbinol or silanol group at the 4-position. As indicated by X-ray diffraction, ¹H NMR spectroscopy, IR spectroscopy, and extensive computational modeling, the OH group of these derivatives is engaged in a bona fide Au···H-O interaction. In addition to shedding light on an elusive bonding situation, these results also indicate that increasing the acidity of the OH functionality is not necessarily beneficial to the stability of the Au(I)···H-O interaction.

Hydrogen bonding to metals as a probe for an inverted ligand field

Electron-rich, late transition metals are known to act as hydrogen-bonding (HBd) acceptors. In this regard, Pt(ii) centres in square-planar environments are particularly efficient. It is however puzzling that no convincing experimental evidence is currently available for the isoelectronic neighbour Au(iii) being involved in HBd interactions. We report now on the synthesis and characterisation of two series of isoleptic and isoelectronic (d8) compounds [(CF3)3Pt(L)]- and (CF3)3Au(L), where the L ligands are based on the quinoline frame and have been selected to favour HBd with the metal centre. Strong HBd interactions were actually found in the Pt(ii) compounds, based on structural and spectroscopic evidence, and they were further confirmed by theoretical calculations. In contrast, no evidence was obtained in the Au(iii) case. In order to find the reason underlying this general disparity, we undertook a detailed theoretical analysis of the model systems [(CF3)3Pt(py)]- and (CF3)3Au(py). This study revealed that the filled dz2 orbital is the HOMO in the case of Pt(ii), but is buried in the lower energy levels in the case of Au(iii). The sharply different electronic configurations involve ligand-field inversion on going from Pt to the next element Au. This is not a gradual but an abrupt change, which invalidates Au(iii) as a HBd-acceptor wherever ligand-field inversion occurs.