Lifetime measurements of ultrashort-lived excited states in Be-like ions

We propose to measure the lifetime of short-lived excited states in highly charged ions by pump-probe experiments. Utilizing two synchronized and delayed Femtosecond pulses allows accessing these lifetimes with Femtosecond precision. Such measurements could provide sensitive tests of state-of-the art atomic structure calculations beyond the capabilities of established methods.     

Phosphorescent Cationic Heterodinuclear IrIII/MI Complexes (M=CuI,AuI) with a Hybrid Janus-Type N-Heterocyclic Carbene Bridge

A novel class of phosphorescent cationic heterobimetallic Ir^III/M^I complexes, where M^I=Cu^I ( 4 ) and Au^I ( 5 ), is reported. The two metal centers are connected by the hybrid bridging 1,3-dimesityl-5-acetylimidazol-2-ylidene-4-olate (IMesAcac) ligand that combines both a chelating acetylacetonato-like and a monodentate N-heterocyclic carbene site coordinated onto an Ir^III and a M^I center, respectively. Complexes 4 and 5 have been prepared straightforwardly by a stepwise site-selective metalation with the zwitterionic [(IPr)M^I(IMesAcac)] metalloproligand (IPr=1,3-(2,6-diisopropylphenyl)-2H-imidazol-2-ylidene) and they have been fully characterized by spectroscopic, electrochemical, and computational investigation. Complexes 4 and 5 display intense red emission arising from a low-energy excited state that is located onto the “Ir(C^N)” moiety featuring an admixed triplet ligand-centered/metal-to-ligand charge transfer (³IL/¹MLCT) character. Comparison with the benchmark mononuclear complexes reveals negligible electronic coupling between the two distal metal centers at the electronic ground state. The bimetallic systems display enhanced photophysical properties in comparison with the parental congeners. Noteworthy, similar non-radiative rate constants have been determined along with a two-fold increase of radiative rate, yielding brightly red-emitting cyclometalating Ir^III complexes. This finding is ascribed to the increased MLCT character of the emitting state in complexes 4 and 5 due to the smaller energy gap between the ³IL and ¹MLCT manifolds, which mix via spin–orbit coupling.     

High-resolution wavelength-dispersive spectroscopy of K-shell transitions in hydrogen-like gold

We present a measurement of K-shell transitions in H-like gold (Au⁷⁸⁺) using specially developed transmission type crystal spectrometers combined with Ge(i) microstrip detectors. The experiment has been carried out at the Experimental Storage Ring at GSI in Darmstadt. This is a first high-resolution wavelength-dispersive measurement of a K-shell transition in a high-Z H-like ion, thus representing an important milestone in this field. Ideas on possible future improvements are discussed as well.     

Fluoro Nitrenoid Complexes FN=MF2 (M=Co,Rh, Ir): Electronic Structure Dichotomy and Formation of Nitrido Fluorides N≡MF3

The fluoronitrenoid metal complexes FNCoF₂ and FNRhF₂ as well as the first ternary Rh^VI and Ir^VI complexes NIrF₃ and NRhF₃ are described. They were obtained by the reaction of excited Group-9 metal atoms with NF₃ and their IR spectra, isolated in solid rare gases (neon and argon), were recorded. Aided by the observed ^14/15N isotope shifts and quantum-chemical predictions, all four stretching fundamentals of the novel complexes were safely assigned. The F−N stretching frequencies of the fluoronitrenoid complexes FNCoF₂ (1056.8 cm⁻¹) and FNRhF₂ (872.6 cm⁻¹) are very different and their N−M bonds vary greatly. In FNCoF₂, the FN ligand is singly bonded to Co and bears considerable iminyl/nitrene radical character, while the N−Rh bond in FNRhF₂ is a strong double bond with comparatively strong σ- and π-bonds. The anticipated rearrangement of FNCoF₂ to the nitrido Co^VI complex is predicted to be endothermic and was not observed.     

Infrared Spectra of the HAnX and H2AnX2 Molecules (An=Th and U,X=Cl and Br) in Argon Matrices Supported by Electronic Structure Calculations

Uranium and thorium hydrides are known as functional groups for ligand stabilized complexes and as isolated molecules under matrix isolation conditions. Here, the new molecular products of the reactions of laser-ablated U and Th atoms with HCl and with HBr, namely HUCl, HUBr and HThCl, HThBr, based on their mid and far infrared spectra in solid argon, are reported. The assignment of these species is based on the close agreement between observed and calculated vibrational frequencies. The H−U and U−³⁵Cl stretching modes of HUCl were observed at 1404.6 and 323.8 cm⁻¹, respectively. Using DCl instead to form DUCl gives absorption bands at 1003.1 and 314.7 cm⁻¹. The corresponding bands of HThCl are 1483.8 (H−Th) and 1058.0 (D −Th), as well as 340.3 and 335.8 cm⁻¹ (Th−³⁵Cl), respectively. HUBr is observed at 1410.6 cm⁻¹ and the BP86 computed shift from HUCl is 6.2 cm⁻¹ in excellent agreement. The U−H stretching frequency increases from 1383.1 (HUF), 1404.6 (HUCl), 1410.6 (HUBr) to 1423.6 cm⁻¹ (UH) as less electronic charge is removed from the U−H bond by the less electronegative substituent. These U−H stretching frequencies follow the Mayer bond orders calculated for the three HUX molecules. A similar trend is found for the Th counterparts. Additional absorptions are assigned to the H₂AnX₂ molecules (An=U, Th, X=Cl, Br) formed by the exothermic reaction of a second HX molecule with the above primary products.     

Synthesis of Aminoboronic Acid Derivatives from Amines and Amphoteric Boryl Carbonyl Compounds

Herein, we demonstrate the use of α‐boryl aldehydes and acyl boronates in the synthesis of aminoboronic acid derivatives. This work highlights the untapped potential of boron‐substituted iminium ions and offers insights into the behavior of N‐methyliminodiacetyl (MIDA) boronates during condensation and tautomerization processes. The preparative value of this contribution lies in the demonstration that various amines, including linear and cyclic peptides, can be readily conjugated with boron‐containing fragments. A mild deprotection of amino MIDA‐boronates enables access to α‐ and β‐aminoboronic acids in high chemical yields. This simple process should be applicable to the synthesis of a wide range of bioactive molecules as well as precursors for cross‐coupling reactions.     

An Electron‐Deficient Azacoronene Obtained by Radial π Extension

A hexapyrrolohexaazacoronene derivative containing 37 fused rings, the largest such system to date, was obtained from a naphthalenomonoimide–pyrrole hybrid in a concise and efficient synthesis. This large heterocycle is electron‐deficient and shows extended redox activity, spanning at least 13 oxidation levels, but is otherwise chemically stable. Radial expansion of the π system creates a chromophore characterized by strong fluorescence and solvatochromism in the neutral state, and strong near‐infrared absorption in the charged states. Additionally, the enlarged and ruffled aromatic surface supports a unique self‐assembly mode in the crystal, leading to the formation of highly solvated organic clathrates.     

Direct Chemical Fine‐Tuning of Electronic Properties in Sc2Ir6−xPdxB

Crystal orbital Hamilton population (COHP) bonding analysis has predicted that ScPd₃B_0.5 is the least stable compound of the entire series Sc₂Ir_6?xPd_xB. Here, we report a systematic study of Sc₂Ir_6?xPd_xB (x=3, 5 and 6) by means of ¹¹B nuclear magnetic resonance (NMR), Knight shift (K) and nuclear spin‐lattice relaxation rate (1/T₁). NMR results combined with theoretical band structure calculations provide a measure of s‐ and non‐s‐character Fermi‐level density of states. We present direct evidence that the enhanced s‐state character of the Fermi level density of states (DOS) in ScPd₃B_0.5 reduces the strength of the B 2p and Pd 4d hybridized states across the entire Sc₂Ir_6?xPd_xB series. This hybridization strength relates to the opening of a deep pseudogap in the density of states of Sc₂IrPd₅B and the chemical bonding instability of ScPd₃B_0.5. This study is an experimental realization of a chemical fine‐tuning of the electronic properties in intermetallic perovskites.