Ligand Influence on the Electronic Spectra of Dicationic Ruthenium-Bipyridine-Terpyridine Complexes

Influence of Metal Identity in Bipyridine-Based Metal-4N Complexes With Formate

We present the vibrational spectra of a series of dicationic, organometallic complexes consisting of a transition metal center (Co, Ni, or Cu) coordinated by 4,4'-di(tert-butyl)-2,2'-bipyridine (DTBbpy) ligands and a formate adduct. Spectral features are analyzed and assigned through comparison with density functional theory calculations, and structures are reported. Natural population analysis shows that the DTBbpy ligands serve as flexible charge reservoirs in each complex. Shifts in the vibrational signatures of the formate moiety reveal that the nature of the metal center plays a crucial role in the charge distribution and formate-metal binding motif in each complex, illustrating the impact of the metal center on the structural and electronic properties of these complexes.

Effects of Formate Binding to a Bipyridine-Based Cobalt-4N Complex

We report the vibrational spectrum of a metal-organic complex consisting of a Co center surrounded by two bipyridine-based ligands and explore the change of the spectrum upon addition of a formate ligand to the complex. We assign the spectra using density functional theory. The infrared response encodes the binding motif of the formate to the metal, and the calculated charge distributions highlight the ability of the organic ligand framework to act as charge reservoirs modulating the redox properties of the metal center.

Spectroscopy and formation of lanthanum-hydrocarbon radicals formed by association and carbon-carbon bond cleavage of isoprene

La atom reaction with isoprene is carried out in a laser-vaporization molecular beam source. The reaction yields an adduct as the major product and C-C cleaved and dehydrogenated species as the minor ones. La(C₅H₈), La(C₂H₂), and La(C₃H₄) are characterized with mass-analyzed threshold ionization (MATI) spectroscopy and quantum chemical computations. The MATI spectra of all three species exhibit a strong origin band and several weak vibronic bands corresponding to La-ligand stretch and ligand-based bend excitations. La(C₅H₈) is a five-membered metallacycle, whereas La(C₂H₂) and La(C₃H₄) are three-membered rings. All three metallacycles prefer a doublet ground state with a La 6s¹-based valence electron configuration and a singlet ion. The five-membered metallacycle is formed through La addition and isoprene isomerization, whereas the two three-membered rings are produced by La addition and insertion, hydrogen migration, and carbon-carbon bond cleavage.

Hydration of a Binding Site with Restricted Solvent Access: Solvatochromic Shift of the Electronic Spectrum of a Ruthenium Polypyridine Complex, One Molecule at a Time

We report the electronic spectra of mass selected [(bpy)(tpy)Ru-OH₂]²⁺·(H₂O)_n clusters (bpy = 2,2'-bipyridine, tpy =2,2':6'2″-terpyridine, n = 0-4) in the spectral region of their metal-to-ligand charge transfer bands. The spectra of the mono- and dihydrate clusters exhibit partially resolved individual electronic transitions. The water network forming at the aqua ligand leads to a rapid solvatochromic shift of the peak of the band envelope: addition of only four solvent water molecules can recover 78% of the solvatochromic shift in bulk solution. The sequential shift of the band shows a clear change in behavior with the closing of the first hydration shell. We compare our experimental data to density function theory (DFT) calculations for the ground and excited states.