Effects of π‐Electron Systems on Optical Activity of Au₁₁ Clusters Protected by Chiral Diphosphines

Abstract

We systematically examined the effects of π‐electron systems on the chiroptical activity of atomically precise gold clusters [Au11(DP)4L2]+, where DP and L represent chiral diphosphines and achiral anionic ligands, respectively. Reducing the distance between the π‐electron systems of the chiral DP and the Au11 core enhanced the anisotropy factor of [Au11(DP)4L2]+ in the range of 300–450 nm while extension of the π‐electron system of the achiral L did not. This tendency supports our previous proposal that the proximity of the chiral π‐electron system to the gold core amplifies the optical activity.

IrAu12superatom modified by chiral diphosphines: doping-induced enhancement of chiroptical activity

“…For these superatoms, the anisotropy factors (g abs and g PL ) are typically of the order of 10 À3 , and the F PL is less than 10%. Previous studies on the crystallization, self-assemby, 11,15,19,21 and doping of superatoms 26 have suggested the following strategies for improving these key parameters: (1) the g abs value can be enhanced via torsion of the superatom 14 and by placing p-electron ligands in the vicinity of the superatom; 10,27 (2) the F PL value can be enhanced through rigidification of the superatom and widening of the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). 26 To test the effectiveness of the above strategies, we herein studied the effects of single-atom doping on the chiroptical properties of a representative Au 13 superatom protected by chiral diphosphine ligands (Chart 1; dppe = 1,2-bis(diphenylphosphino)ethane, DIPAMP = 1,2-bis[(2-methoxyphenyl)phenylphosphino]ethane), i.e., [Au 13 ((R,R)-DIPAMP) 5 Cl 2 ] 3+ (Au 13 -R) and [Au 13 ((S,S)-DIPAMP) 5 Cl 2 ] 3+ (Au 13 -S).…”

“…For these superatoms, the anisotropy factors ( g abs and g PL ) are typically of the order of 10 −3 , and the Φ PL is less than 10%. Previous studies on the crystallization, self-assemby, 11,15,19,21 and doping of superatoms 26 have suggested the following strategies for improving these key parameters: (1) the g abs value can be enhanced via torsion of the superatom 14 and by placing π-electron ligands in the vicinity of the superatom; 10,27 (2) the Φ PL value can be enhanced through rigidification of the superatom and widening of the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). 26…”

Copper Nanocluster Enables Simultaneous Photodynamic and Chemo Therapy for Effective Cancer Diagnosis and Treatment in Vitro

“…These metal clusters show size-dependent fluorescence near the Fermi wavelength of electrons. [33][34][35][36] This inherent fluorescence property of Au, Ag, and Cu clusters is utilized for the diagnosis of cancer. Protoporphyrin conjugated gold clusters were utilized for the diagnosis and treatment of cancer cells.…”

“…were explored due to the unique geometric and electronic properties. These metal clusters show size‐dependent fluorescence near the Fermi wavelength of electrons [33–36] . This inherent fluorescence property of Au, Ag, and Cu clusters is utilized for the diagnosis of cancer.…”

Influence of Halogen–Solvent Hydrogen Bonding on Gold Nanocluster Photoluminescence

“…These clusters are especially malleable, with ligand substitutions causing significant deformations to the MPC core structure. , Replacement of monodentate phosphine ligands with bidentate ones transforms the normally achiral cluster to a chiral geometry . The chiral cluster shows rich circular dichroism (CD) spectra, spanning ultraviolet–visible (UV–vis) frequencies. ,, Because in the bidentate case the same ligand is bound to the gold core at two sites, strain is imparted onto the gold kernel and in turn alters the bond lengths and rigidity of the metal. Density functional theory (DFT) calculations also indicate that ligands that passivate these clusters have a significant impact on the electronic structure and chiroptical properties of the gold core. , …”