The electronic spectra of ThF and ThF(+) have been examined using laser induced fluorescence and resonant two-photon ionization techniques. The results from high-level ab initio calculations have been used to guide the assignment of these data. Spectra for ThF show that the molecule has an X (2)Δ(3/2) ground state. The upper spin-orbit component, X (2)Δ(5/2) was found at an energy of 2575(15) cm(-1). The low-lying states of ThF(+) were probed using dispersed fluorescence and pulsed field ionization-zero kinetic energy (PFI-ZEKE) photoelectron spectroscopy. Vibronic progressions belonging to four electronic states were identified. The lowest energy states were clearly (1)Σ(+) and (3)Δ(1). Although the energy ordering could not be rigorously determined, the evidence favors assignment of (1)Σ(+) as the ground state. The (3)Δ(1) state, of interest for investigation of the electron electric dipole moment, is just 315.0(5) cm(-1) above the ground state. The PFI-ZEKE measurements for ThF yielded an ionization energy of 51 581(3) cm(-1). Molecular constants show that the vibrational constant increases and the bond length shortens on ionization. This is consistent with removal of a non-bonding Th-centered 6d or 7s electron. Laser excitation of ThF(+) was used to probe electronically excited states in the range of 19,000-21,500 cm(-1).

Understanding the influence of electrons in partially filled f- and d-orbitals on bonding and reactivity is a key issue for actinide chemistry. This question can be investigated by using a combination of well-defined experimental measurements and theoretical calculations. Gas phase spectroscopic data are particularly valuable for the evaluation of theoretical models. Consequently, the primary objectives of our research have been to obtain gas phase spectra for small actinide molecules. To complement the experimental effort, we are investigating the potential for using relativistic ab initio calculations and semiempirical models to predict and interpret the electronic energy level patterns for f-element compounds. Multiple resonance spectroscopy and jet cooling techniques have been used to unravel the complex electronic spectra of Th and U compounds. Recent results for fluorides, sulfides, and nitrides are discussed.

Rotationally resolved spectra for Be(2) (+) have been recorded using the pulsed-field ionization zero kinetic energy photoelectron technique. Vibrational levels in the range v(+)=0-6 were observed. The rotational selection rules confirmed that the ground state is (2)Sigma(u) (+), resulting from the removal of an electron from the sigma(u) antibonding orbital of Be(2). The bond energy and equilibrium distance for Be(2) (+) were found to be D(e) (+)=16 438(5) cm(-1) and R(e) (+)=2.211(8) A. The ionization energy for Be(2) [59 824(2) cm(-1)] was also refined by these measurements. Comparisons with high-level theoretical results indicate that the bonding in Be(2) (+) is adequately described by multi reference singles and doubles configuration interaction (MRDCI) calculations that employ moderate to large scale basis sets.

The properties of the HfF+ cation are thought to be well-suited for investigations of the electron electric dipole moment (eEDM) and temporal variations of the fine structure constant. Precision spectroscopic measurements involving the X1Σ+ and low-lying 3Δ1 states have been proposed to measure both. Due to the lack of data for HfF+, the design of these experiments has relied entirely on the predictions of electronic structure calculations. Spectroscopic characterizations of the X1Σ+, 3Δ1, 3Δ2 and 3Δ3 states are reported. The results further support the contention that HfF+ is a viable candidate for eEDM measurements. The spacings between adjacent X1Σ+ and 3Δ1 levels are found to be less favorable for the proposed studies of the fine structure constant.

Visible and near-infrared illumination induces 5f-5f and ligand-to-metal charge-transfer (LMCT) transitions of the neptunyl tetrachloride anion in polycrystalline Cs 2 U(Np)O 2 Cl 4 , and results in near-infrared luminescence from the second electronically excited state to the ground state. This photoluminescence is used as a detection method to collect excitation spectra throughout the near-infrared and visible regions. The excitation spectra of LMCT transitions in excitation spectra were identified in previous work. Here the measurement and analysis is extended to include both LMCT and intra-5f transitions. The results manifest variation in structural properties of the neptunium-oxo bond among the lowlying electronic states. Vibronic intensity patterns and energy spacings are used to compare bond lengths and vibrational frequencies in the excited states, confirming significant characteristic differences between those excited by 5f-5f transitions from those due to LMCT transitions. Results are compared with recently published SO-RASPT2 calculations of [NpO 2 Cl 4 ] 2- .

A new tetrathiafulvalene-salphen uranyl complex has been prepared. The system was designed to study the electronic coupling between actinides and a redox active ligand framework. Theoretical and experimental methods -including DFT calculations, single crystal X-ray analysis, cyclic voltammetry, NMR and IR spectroscopies -were used to characterize this new uranyl complex.A large number of complexes based on organic donor tetrathiafulvalene (TTF) ligands and 3d transition metal centers are known. 1 Complementing studies of these systems are recent efforts to develop TTF-containing complexes of the lanthanide cations. 2 To the best of our knowledge this work has not been extended to the actinide series.Early actinides are typically characterized by more radially extended and accessible f orbitals compared to the lanthanides. Accordingly, substitution of a lanthanide ion for an actinide in a redox active ligand framework offers an opportunity to enhance electronic communication between the ligand and the coordinated metal. 3 Here, we report a uranyl complex (1) based on a TTF-functionalized N,N′-phenylenebis(salicylideneimine) analogue (i.e., TTF salphenH 2 ). Although complex 1 contains a diamagnetic ion, characterizing the interactions between UO 2 2+ and the TTF-ligand represents a crucial first step towards subsequent experiments involving paramagnetic actinyls. Complex 1 was analyzed using a combination of theoretical, electrochemical, and spectroscopic methods. Taken in concert, these studies support the notion that communication between an actinyl cation and a redox active ligand can be achieved. They thus set the stage for more technically challenging studies involving related species such as the PuO 2 2+ cation.The present strategy for obtaining actinide complexes based on TTF-functionalized ligands involves coordinating a uranyl cation to an N,N′-phenylenebis(salicylideneimine) salphentype ligand, specifically the known TTF-salphen dianion ( TTF salphen 2− ). 4 The TTF part of the TTF salphen 2− dianion is redox active and capable of two reversible one-electron oxidations, while the salphen portion of the ligand provides a tetradentate binding site extensively used in actinide science for stabilizing multiple uranium oxidation states (U 4+ , UO 2 1+ , UO 2 2+ ). 3f,5 Complex 1 was thus deemed attractive as a platform for examining electronic coupling effects involving actinide elements and redox active ligands. The synthesis of complex 1 is shown in Scheme 1. Briefly, reacting bis( propylthio)-TTF-benzo-o-diamine 6 with salicylaldehyde and UO 2 (NO 3 ) 2 ·6H 2 O in ethanol provided complex 1 as a red solid in 73% yield. ‡ The 1 H NMR spectrum of this new product was consistent with the uranyl center being complexed by the TTF salphen 2− ligand (see ESI †). 4 Complex 1 (as its methanol complex) was unambiguously characterized in the solid-state via an X-ray crystallographic analysis. Suitable crystals for the analysis were obtained by slow evaporation of a solution of complex 1 in a 1 : 1 mixture of CH 2 C...

The ground electronic state of BeOBe(+) was probed using the pulsed-field ionization zero electron kinetic energy photoelectron technique. Spectra were rotationally resolved and transitions to the zero-point level, the symmetric stretch fundamental and first two bending vibrational levels were observed. The rotational state symmetry selection rules confirm that the ground electronic state of the cation is (2)Σ(g)(+). Detachment of an electron from the HOMO of neutral BeOBe results in little change in the vibrational or rotational constants, indicating that this orbital is nonbonding in nature. The ionization energy of BeOBe [65480(4) cm(-1)] was refined over previous measurements. Results from recent theoretical calculations for BeOBe(+) (multireference configuration interaction) were found to be in good agreement with the experimental data.

Electronic spectra for BeC have been recorded over the range 30,500-40,000 cm(-1). Laser ablation and jet-cooling techniques were used to obtain rotationally resolved data. The vibronic structure consists of a series of bands with erratic energy spacings. Two-color photoionization threshold measurements were used to show that the majority of these features originated from the ground state zero-point level. The rotational structures were consistent with the bands of (3)Π-X(3)Σ(-) transitions. Theoretical calculations indicate that the erratic vibronic structure results from strong interactions between the four lowest energy (3)Π states. Adiabatic potential energy curves were obtained from dynamically weighted MRCI calculations. Diabatic potentials and coupling matrix elements were then reconstructed from these results, and used to compute the vibronic energy levels for the four interacting (3)Π states. The predictions were sufficiently close to the observed structure to permit partial assignment of the spectra. Bands originating from the low-lying 1(5)Σ(-) state were also identified, yielding a (5)Σ(-) to X(3)Σ(-) energy interval of 2302 ± 80 cm(-1) and molecular constants for the 1(5)Π state. The ionization energy of BeC was found to be 70,779(40) cm(-1).