Geometric and Electronic Structures of Ag⁺(benzo-18-crown-6), Ag⁺(dibenzo-18-crown-6), and Ag⁺(dibenzo-15-crown-5) Complexes Investigated by Cold Gas-Phase Spectroscopy

Abstract

The UV photodissociation (UVPD) spectra of Ag + complexes with benzo-18-crown-6 (B18C6), dibenzo-18crown-6 (DB18C6), and dibenzo-15-crown-5 (DB15C5) [Ag + (B18C6), Ag + (DB18C6), and Ag + (DB15C5)] are observed under cold gas-phase conditions. Ag + (B18C6) and Ag + (DB18C6) show sharp vibronic bands in the 36000− 37200 cm − 1 region, while the UVPD spectrum of Ag + (DB15C5) is very broad. These UV bands are assigned to the π−π* transition, which is localized on the B18C6, DB18C6, and DB15C5 part of the complexes. Quantum chemical calculations suggest that the broad UV feature of Ag + (DB15C5) can be attributed to the short lifetimes of optically excited ππ* states due to internal conversion (IC) to low-lying excited states that are present only for this complex. The appearance of the π−π* transition in the same UV region as that of the neutral crown ethers and their complexes with alkali metal ions indicates that the positive charge is localized on the Ag atom in these complexes. However, the fragment ions produced after UV absorption are B18C6 + , DB18C6 + , and DB15C5 + radical ions, indicating that they are produced via charge transfer (CT) between the Ag + ion and benzo-crown ethers. The CT during fragmentation is attributed to the higher ionization energy of Ag atom when compared to the benzo-crown ethers. In the complexes, the Ag + ion is effectively encapsulated by the crown cavity of the benzo-crown ethers without transferring the positive charge from Ag + to the crown. However, UV excitation of the Ag + (B18C6), Ag + (DB18C6), and Ag + (DB15C5) complexes can reduce the Ag + ion and produce a Ag atom with high efficiency in the gas phase.

Effect of the Presence of Oxysolvents on Compositions and Structures of Silver(I) Complexes with Boron Cluster Anion [B12Cl12]2–

“…The effect of the anion on the structures of a number of interesting silver coordination polymers [Ag 12 (m-O-mi) 2 ]-ClO 4 , [Ag 12 (m-O-mi) 2 ]SbF 6 , [Ag 12 (m-O-mi)(NO 3 ) 2 ] 38 was studied. A number of works are devoted to the study of weak interactions in the presence of crown ethers, in which the metal atom is both embedded inside 39 and located between two separate molecules {[Ag(12-crown-4) 2 ][AsF 6 ]} 40 or {[Ag(15crown-5) 2 ][SbF 6 ]}. 41 The research carried out in these works allows us to expand our fundamental understanding of complex formation processes associated with ligand metathesis.…”

Intra-host π–π interactions in crown ether complexes revealed by cryogenic ion mobility-mass spectrometry

“…[33][34][35][36] Nuclear magnetic resonance studies of structures of the conformations of the dibenzo-30-crown-10 (DB30C10) complexes with alkali metal ions, M (M = Na and K), M + (DB30C10), in solution also showed the same configuration of DB30C10 as that reported for the crystal. 37,38 The conformation of the crown ether complexes in the gas phase was studied by ultraviolet photodissociation (UVPD) 26,[39][40][41][42][43][44][45][46] and IM-MS. [8][9][10][26][27][28][29][30] Previously, we studied the conformations of M + (DB24C8) (M = Na, K, Rb, and Cs) using cryogenic IM-MS. The coexistence of two conformers, open and closed conformers, were confirmed in the study, which have long and short distances between the two benzene rings in a molecule, respectively.…”

Conformation of Benzo-12-Crown-4 Complexes with Ammonium Ions Investigated by Cold Gas-Phase Spectroscopy

“…The conformation of the CE complexes was initially investigated using X-ray diffraction of the crystals. Recently, gas-phase IR spectroscopy was performed to reveal the conformation of the CE complexes with metal ions. − For benzo-CE complexes, UV spectroscopy under cold gas-phase conditions provided information on the conformation. − These complexes showed sharp vibronic structures in their UV spectra, allowing the application of UV–UV and IR–UV double-resonance spectroscopy to examine the number of conformers and their structures. For molecular ion guests, ammonium ions containing the NH 3 + group also form stable complexes with CEs. ,− For CE complexes with molecular ion guests, IR spectroscopy in the gas phase was performed for ammonium ions and protonated amino acids. ,, Recently, we studied dibenzo-18-crown-6 (DB18C6) complexes with primary alkylammonium ions (RNH 3 + ) by cold UV spectroscopy in the gas phase .…”