Interpretation of size evolution is an essential part of nanocluster transformation processes for unraveling the mechanism at an atom-precision level. Here we report the transformation of a nonsuperatomic Au 23 to a superatomic Au 36 nanocluster via Au 28 cluster formation, activated by the bulky 4-tert-butylbenzenethiol ligand. Time-dependent matrix-assisted laser desorption ionization mass spectrometry data revealed that the conversion proceeds through ligand exchange followed by the size focusing method, ultimately leading to size growth. We also validated this transformation through time-dependent ultraviolet−visible data. Density functional theory calculations predicted that the kernel of the Au 28 cluster evolved through a linear combination of molecular orbitals of the fragment of 2e − units (Au 4 2+ and Au 3 + ) from the kernel of the Au 23 cluster. Periodic growth of gold cores through continuous growth of Au 4 tetrahedral unit leads to the formation of the Au 36 cluster from the Au 28 cluster. These results reinforce the plausibility of size evolution through the growth mechanism during the transformation process. Differential pulse voltammetry studies showed that the highest occupied molecular orbital−lowest unoccupied molecular orbital gap inversely varies with the kernel size of these clusters. Photophysical experiments support the molecular-like intersystem crossing rather than core−shell relaxation to these clusters. The trends of photoluminescence lifetime were found to be the reverse of those of the energy gap law. The increment of lifetimes for the larger cluster can be mainly due to the contribution of both hot carriers and band-edge carriers.

We report the ligand-exchange-induced transformation from an icosahedral Au 25 (SR) 18 cluster (where SR = 2-phenylethanethiol (PET)) to a bitetrahedral Au 22 (SR) 4 (SR′) 14 cluster (where SR′ = 4-tert-butylbenzenethiol (TBBT)). This partial exchange of the ligands was achieved by controlling the concentration of the incoming TBBT ligand. Being a bulky and aromatic ligand, TBBT can efficiently distort the atomic structure of the Au 25 PET 18 cluster, resulting in Au 22 (PET) 4 (TBBT) 14 , which is highly stable and considered to be an intermediate with a bitetrahedral structure. Time-dependent mass spectrometry and optical spectroscopy revealed the dissociation of the parent cluster and gave a deep insight on the ligand-exchange mechanism. Theoretical calculations and extended Xray absorption fine structure studies confirm the formation of the Au 22 structure. Identifying the atomic structure of the intermediate species opens a new avenue to study the transformation of one cluster to another.

The symmetry of atomically precise nanoclusters is influenced by the specific geometry of the kernel and the arrangement of staple motifs. To understanding the role of ligand and its effect on the breaking of symmetry during ligand exchange transformation, it is necessary to have a mechanism of transformation in an atomically precise manner. Herein, we report the structural transformation from bipyramidal kernel to icosahedral kernel via ligand exchange. The transformation of [Au23(CHT)16]− to [Au25(2-NPT)18]− through ligand (aromatic) exchange revealed two important principles. First, the combined effort of experimental and theoretical study on structural analysis elucidated the mechanism of this structural transformation where “bridging thiolate” and “hub” gold atoms play a crucial role. Second, we have found that the higher crystal symmetry of the Au23 cluster is broken to lower crystal symmetry during the ligand exchange process. This showed that during ligand exchange, the hub atoms and μ3-S atoms get distorted and contributed to the ligand-staple motif formation. These phenomena specified that the ligand effects might be the pivotal factor to impose lower symmetry of the crystal system in the product clusters.

Engineering defective UiO-66 with functionalized modulator may create functionality with promising physical and chemical properties. Herein, we use 2-mercaptobenzoic acid (2-MBA) as a modulator for the functionalization of defective UiO-66...

The fixing of N 2 to NH 3 is challenging due to the inertness of the N�N bond. Commercially, ammonia production depends on the energy-consuming Haber-Bosch (HÀ B) process, which emits CO 2 while using fossil fuels as the sources of hydrogen and energy. An alternative method for NH 3 production is the electrochemical nitrogen reduction reaction (NRR) process as it is powered by renewable energy sources. Here, we report a tiara-like nickel-thiolate cluster, [Ni 6 (PET) 12 ] (where, PET = 2-phenylethanethiol)] as an efficient electro-catalyst for the electrochemical NRR at ambient conditions. Ammonia (NH 3 : 16.2 � 0.8 μg h À 1 cm À 2 ) was the only nitrogenous product over the potential of À 2.3 V vs. F c + /F c with a Faradaic efficiency of 25% � 1.7. Based on theoretical calculations, NRR by [Ni 6 -(PET) 12 ] proceeds through both the distal and alternating pathways with an onset potential of À 1.84 V vs. RHE (i.e., À 2.46 V vs. F c + /F c ) which corroborates with the experimental findings.