In this work, La atom reactions with small alkylamines R−NH₂ and H₂N−(CH₂)_n−NH₂ (n=2, 3, 4) are carried out in a laser-ablation supersonic molecular beam source. Reaction products are observed with photoionization time-of-flight mass spectrometry and characterized by mass-analyzed threshold ionization (MATI) spectroscopy and DFT calculations. These reactions proceed via an exothermic H₂ loss from the ligand and form a metal complex. The R−NH₂ ligands favor the formation of acyclic metal complexes where La atom is doubly bonded to the N atom, whereas the H₂N−(CH₂)_n−NH₂ ligands prefer the formation of cyclic metal complexes where La atom is bonded to both N atoms. The reaction between La atom and CH₃NH₂ produces LaNCH₃ in two low-energy isomeric forms: an acyclic C_3v structure and a three -membered C_s ring. The C_3v isomer is formed by concerted elimination of two H atoms from the NH₂ group, whereas the C_s ring is formed by H atom elimination from both the alpha C and NH₂ group. Both isomers prefer a doublet ground state with a La 6s¹-based electron configuration and a singlet ionic state by removing the 6s electron. The C_3v structure is calculated to be more stable than the C_s isomer but has a slightly lower adiabatic ionization energy (40022 (5) cm⁻¹) than the ring isomer (40399 (5) cm⁻¹) as measured from the MATI spectra. The MATI spectrum of the C_3v isomer is dominated by the origin band and La-Ligand and C-N stretching vibronic bands. The MATI signal of the C_s isomer is very weak and is only 10% of the C_3v MATI signal. This observation confirms that the C_3v isomer is more stable and its formation is more favorable than the C_s ring.

Bimetallic catalysts have attracted great research efforts in the past decades due to their chemical and physical properties different from the individual pure metals and promising applications in chemical conversion, energy technology and environmental protection. Numerous experimental and theoretical investigations have been focused on the reactions of transition metal atoms and small clusters with CO, and a variety of transition-metal carbonyl complexes have been characterized in gas phase and in solid argon. Since they are a very few studies on the transition metal heteronuclear dimer, we have studied in solid argon the reactivity of carbon monoxide with the heterodimer PdTi by infrared spectroscopy (FTIR). Heteronuclear cluster carbonyls, PdTi(CO)_n (n=1-3) and Pd₂Ti(CO)₂, have been characterized on the basis of the isotopic substitution and irradiation effect. DFT calculations of the geometrical and electronic properties are also presented, and compared with the experimental values. An irradiation in visible leads to conversion between the isomers Pd-Ti-CO and Ti-Pd-CO distinguished by a large shift of the stretching frequency of the diatomic CO.

We perform, for the first time, gas-phase laser photodissociation spectroscopy on a series of metal carbonyls that can lose CO upon irradiation. These molecules (PhotoCORMs) can be used for delivering and releasing CO molecules for medicinal purposes, such as in cancer therapy and as antimicrobials. Photodepletion (PD) and photofragmentation (PF) spectra of [CpRu(Ph₃)₂CO]⁺ and [CpRu(dppe)CO]⁺ were acquired between 230 and 400 nm, and the range 230-500 nm was explored for [Mn(CO)₄Br₂]⁻. All the PhotoCORMs lose CO after irradiation, accessing different fragmentation channels when different excited states are populated. Indeed, while scanning the wavelength range in our laser-interfaced electrospray mass spectrometer, we observe the production spectra of the photofragments and can track the variation in the intensity of their production. [Mn(CO)₄Br₂]⁻ loses 3 CO molecules in the key visible region and 4 COs in the UV. [CpRu(Ph₃)₂CO]⁺ fragments into [CpRuPh₃]⁺ via the loss of CO and Ph₃. This observation can be used to improve the design of new CO-releasing molecules, as we demonstrate in the [CpRu(dppe)CO]⁺ system where we successfully observe only the CO loss across the whole explored wavelength range. Finally, solution-phase irradiation results are presented for 365 nm photoexcitation, showing comparable photofragmentation results to the ones obtained in the gas-phase.

Sub-100 fs time-resolved, broadband transient absorption spectroscopy was employed to investigate ultrafast radiationless relaxation dynamics of near-infrared, metal-centered (MC), electronic excited states of several d⁵ and d⁹ transition metal complexes (e.g., CuCl₄²⁻, CuBr₄²⁻, IrBr₆²⁻, IrCl₆²⁻, etc.) in acetonitrile solution. The results yield insights into the topology of the involved potential energy surfaces, Jann-Teller distortions, and the dynamics through conical intersections connecting the first excited and ground electronic states (energy gap, less than 8000 cm⁻¹). Furthermore, it was found that the addition of water to the solutions efficiently quenches the MC excited states via energy transfer.

Beryllium can exhibit unusually strong attractive interactions under conditions where it is nominally a closed-shell atom. Two prominent examples are the Be₂ dimer and the He-BeO complex. Most recently, we examined the bonding of a similarly interesting molecule, the closed-shell Be-F⁻ anion. This molecule preserves the closed-shell character of the atoms as the electron affinity of F is high (328.16 kJ mol⁻¹) while that of Be is negative. Photoelectron velocity map imaging spectroscopy, in conjunction with coupled cluster electronic structure calculations, were used to determine the vibrational frequency for BeF⁻ and the electron affinity of BeF (approximately 8700 cm⁻¹). The latter has been used to determine a lower bound of 28480 cm⁻¹(343 kJ mol⁻¹) for the bond energy of BeF⁻. The electronic structure calculations yielded predictions that were in good agreement with the observed data. A natural bond orbital analysis shows that BeF⁻ is primarily bound by a dative interaction.

TiO is a molecule of considerable astronomical importance. It is present in the atmospheres of oxygen-rich low-mass stellar objects. Three Fourier transform emission spectra have been used to determine improved and consistent spectroscopic constants of the a¹∆, b¹Π, d¹Σ⁺, c¹Φ and f¹∆ states of TiO by fitting the b¹Π-a¹∆, b¹Π- d¹Σ⁺, c¹Φ-a¹∆ and f¹∆-a¹∆ systems. This analysis provides the most extensive fit of the TiO singlet states. New bands of the b¹Π-a¹∆ and c¹Φ-a¹∆ systems have been measured and an extensive list of line positions will be published.

The [7.7] Y ²Σ⁺ - X ²Π_i transition of CuO was observed in emission from a Cu hollow cathode recorded with the FT-spectrometer associated with the McMath-Pierce Solar Telescope at Kitt Peak in 1994. In 1996, a rotational analysis of the (0,0) band of the Y - X transition was reported by O’Brien et al. In a recent analysis of the (0,0) and (1,1) bands of the [16.4] A ²Σ⁻ - X ²Π_i transition of CuO performed by the authors, improved centrifugal distortion constants for the X ²Π_i state were obtained. Line positions from the millimeter wave spectrum of CuO reported by Steimle et al. were successfully incorporated into the fit of the A – X transition, however, a fit including the line positions of the Y - X transition reported by O’Brien et al. showed small, yet significant, deviations in the residuals of the fit. In this study, the FTS data from 1994 was accessed from the FTP archive available from the National Solar Observatory website to investigate these deviations. The calibration of the data was verified to ±0.001 cm⁻¹using Ne reference lines from Sansonetti et al. Using PGOPHER simulations and the improved rotational constants for the X ²Π_i ground state, over 1000 additional line positions belonging to the (0,0) band of the Y - X transition were identified in the FTS data. Several previously unidentified vibrational bands were also observed and rotationally analyzed using PGOPHER, specifically the (2,0), (2,1), (2,2), (2,3), (1,0), (1,1), (1,2), (1,3), (0,0), (0,1), and (0,2) bands. A comprehensive fit of the data containing more than 10,000 line positions has been conducted using PGOPHER. The fit successfully incorporated the millimeter wave data for the X ²Π_i state from Steimle et al. and the intracavity laser absorption data for the A - X state from the authors. Results of this analysis will be presented.

An electronic transition of CuOH has been observed in the red using Intracavity Laser Spectroscopy (ILS). The CuOH molecules were produced in the 0.60 A RF-discharge of a Cu hollow cathode using either 1 Torr of H₂ and 200 mTorr of O₂ as sputter gases to produce CuOH, or 800 mTorr of O₂ and 200 mTorr of D₂ to produce CuOD. The hollow cathode was located in the resonator cavity of a dye laser, enabling the enhancement of molecular absorption features through laser action. Using a generation time of 200 μsec and a 130 mm long cathode, the effective pathlength for the measurements was approximately 7 km. Each 6 cm⁻¹wide spectral segment was calibrated by fitting I₂ absorbance features from spectra collected from an extracavity I₂ cell at each monochromator position (with the plasma turned off) to the I₂ reference data of Salami and Ross. Deviations between the recorded and reference I₂ features were typically less than ±0.002 cm⁻¹. Two strong red-degraded Q-bandheads are observed in the CuOH spectrum, located at 15,155 cm⁻¹and 15,093 cm⁻¹. These bands are consistent with an electronic transition briefly mentioned but not analyzed in a publication on the A ¹A'-X ¹A' transition of CuOH by Jarman et al. from 1991. The isotopologue shifts of the CuOD Q-heads are +4.5 cm⁻¹and +5.0 cm⁻¹, respectively. The transitions for both isotopologues have P-, Q-, and R-branches with no observed splitting. Each branch is accompanied by features due to ⁶⁵CuOH that are approximately 40% of the intensity of the main features, consistent with natural abundances of 69.17% ⁶³Cu and 30.83% ⁶⁵Cu. Ground state constants for CuOH and CuOD are determined from the millimeter wave spectra of Whitham et al., and the transitions will be fit using PGOPHER. Results of the analysis will be presented.