Organic ligands on gold nanoclusters play important roles in regulating the structures of gold cores. However, the impact of the number and positions of the protecting ligands on gold-core structures remains unclear. We isolated thiolate-protected Au 25 cluster anions, [Au 25 (SC 2 Ph) 17 (Por) 1 ] − and [Au 25 (SC 2 Ph) 16 (Por) 2 ] − (SC 2 Ph = 2-phenylethanethiolate), obtained by ligand exchange of [Au 25 (SC 2 Ph) 18 ] − with one or two porphyrinthiolate (Por) ligands as mixtures of regioisomers. The ratio of two regioisomers in [Au 25 (SC 2 Ph) 17 (Por) 1 ] − as measured by 1 H NMR spectroscopy revealed that the selectivity could be controlled by the steric hindrance of the incoming thiols. Extended X-ray absorption fine structure studies of a series of porphyrin-coordinated gold nanoclusters clarified that the Au 13 icosahedral core in the Au 25 cluster was distorted through steric repulsion between porphyrin thiolates and phenylethanethiolates. This paper reveals interesting insights into the importance of the steric structures of protecting ligands for control over core structures in gold nanoclusters.

Surface defects are pervasive in quantum dots (QDs) and are detrimental to their applications. The recycling of trapped excitons is key for the efficient utilization of QDs, while the strategy for this is limited. Here, we discovered a unique recycling process for deep trapped excitons in molecule-coordinated defect-rich QD systems. Triplet–triplet energy transfer (TTET) from defect-rich QDs to surface-attached perylene-3-carboxylic acid (Pe) was investigated at a low temperature (77 K), and the contribution of defect state was suggested the Auger-assisted recycling process of the defect-trapped carriers, having insufficient energy for TTET. The discovery of TTET via exciton recycling from defects provides a new way to reuse untapped excitons in QDs and QD devices.

Isomer-selective conversion is a challenging goal in the rational design of Au clusters. Herein, we demonstrate the isomer-selective conversion of Au 18 (ScC 6 ) 14 (ScC 6 = cyclohexanethiolate) into Au 24 (SR) x (ScC 6 ) 20−x in high yields by reactions with gold(I) thiolate (AuSR) complexes. Electrospray ionization mass spectrometry indicated that even numbers of AuSR units are inserted into Au 18 (SR) x (ScC 6 ) 14−x to generate Au 24 (SR) x (ScC 6 ) 20−x through intermediates Au 20 (SR) x (ScC 6 ) 16−x or Au 22 (SR) x (ScC 6 ) 18−x . These results suggest that the number of constituent atoms in surface Au(I)SR oligomers only increases, while the number of electrons in an Au core is maintained. UV−vis analysis revealed the generation of one of two Au 24 (SR) x (ScC 6 ) 20−x isomers in the reactions of Au 18 (ScC 6 ) 14 with AuSR complexes, in contrast to the formation of both isomers by reactions with thiols. When the structures of Au 18 (SR) 14 are compared with those of the Au 24 (SR) 20 isomers, the partial structure in the Au cores is preserved in the isomer-selective conversion with AuSR complexes, regardless of the structures of the thiolate moiety.