Zwitterions Functionalized by Optical Cycling Centers: Toward Laser-Coolable Polyatomic Molecular Cations

Functionalization of large aromatic compounds and biomoleculeswith optical cycling centers (OCC) is of considerable interest forthe design and engineering of molecules with a highly selective opticalphotoresponse. Both internal and external dynamics in such moleculescan be precisely controlled by lasers, enabling their efficient coolingand opening up broad prospects for high-precision spectroscopy, ultracoldchemistry, enantiomer separation, and various other fields. The waythe OCC is bonded to a molecular ligand is crucial to the opticalproperties of the OCC, first of all, for the degree of closure ofthe optical cycling loop. Here we introduce a novel type of functionalizedmolecular cation where a positively charged OCC is bonded to variousorganic zwitterions with a particularly high permanent dipole moment.We consider strontium(I) complexes with betaine and other zwitterionicligands and show the possibility of creating efficient and highlyclosed population cycling for dipole-allowed optical transitions insuch complexes.

Automated summary

Functionalization of large aromatic compounds and biomolecules with optical cycling centers (OCC) enables precise control of internal and external dynamics, leading to applications in high-precision spectroscopy, ultracold chemistry, and enantiomer separation. This study introduces a novel type of functionalized molecular cation with a positively charged OCC bonded to organic zwitterions, showing efficient and highly closed population cycling for dipole-allowed optical transitions in strontium(I) complexes with betaine and other zwitterionic ligands.