Upgrade of the SPECIES beamline at the MAX IV Laboratory

Abstract The SPECIES beamline has been transferred to the new 1.5 GeV storage ring at the MAX IV Laboratory. Several improvements have been made to the beamline and its endstations during the transfer. Together the Ambient Pressure X-ray Photoelectron Spectroscopy and Resonant Inelastic X-ray Scattering endstations are capable of conducting photoelectron spectroscopy in elevated pressure regimes with enhanced time-resolution and flux and X-ray scattering experiments with improved resolution and flux. Both endstations offer a unique capability for experiments at low photon energies in the vacuum ultraviolet and soft X-ray range. In this paper, the upgrades on the endstations and current performance of the beamline are reported

A low-spin Fe(iii) complex with 100-ps ligand-to-metal charge transfer photoluminescence

Transition-metal complexes are used as photosensitizers1, in light-emitting diodes, for biosensing and in photocatalysis2. A key feature in these applications is excitation from the ground state to a charge-transfer state3,4; the long charge-transfer-state lifetimes typical for complexes of ruthenium5 and other precious metals are often essential to ensure high performance. There is much interest in replacing these scarce elements with Earth-abundant metals, with iron6 and copper7 being particularly attractive owing to their low cost and non-toxicity. But despite the exploration of innovative molecular designs6,8,9,10, it remains a formidable scientific challenge11 to access Earth-abundant transition-metal complexes with long-lived charge-transfer excited states. No known iron complexes are considered12 photoluminescent at room temperature, and their rapid excited-state deactivation precludes their use as photosensitizers13,14,15. Here we present the iron complex [Fe(btz)3]3+ (where btz is 3,3′-dimethyl-1,1′-bis(p-tolyl)-4,4′-bis(1,2,3-triazol-5-ylidene)), and show that the superior σ-donor and π-acceptor electron properties of the ligand stabilize the excited state sufficiently to realize a long charge-transfer lifetime of 100 picoseconds (ps) and room-temperature photoluminescence. This species is a low-spin Fe(iii) d5 complex, and emission occurs from a long-lived doublet ligand-to-metal charge-transfer (2LMCT) state that is rarely seen for transition-metal complexes4,16,17. The absence of intersystem crossing, which often gives rise to large excited-state energy losses in transition-metal complexes, enables the observation of spin-allowed emission directly to the ground state and could be exploited as an increased driving force in photochemical reactions on surfaces. These findings suggest that appropriate design strategies can deliver new iron-based materials for use as light emitters and photosensitizers

Adsorption of Dipyrrin-Based Dye Complexes on a Rutile TiO 2

The adsorption of two ruthenium-based dye complexes containing dipyrrin-based ligands has been studied on the rutile TiO2(110) surface using synchrotron-based electron spectroscopy. The dye complexes studied were bis(5-(4-carboxyphenyl)-4,6-dipyrrin)bis(dimethyl sulfoxide)ruthenium(II) and bis(5-(4-carboxyphenyl)-4,6-dipyrrin)(2,2′-bipyridine)ruthenium(II). The dye molecules were deposited using in situ electrospray deposition, which allows for the deposition of thermally fragile molecules in ultrahigh vacuum. Photoemission studies were used to provide experimental data on the bonding geometry of the dye complexes to the rutile TiO2(110) substrate and to provide data on molecular orbitals involved in the charge transfer process. DFT calculations of the molecules adsorbed onto the rutile TiO2(110) surface have also been performed to identify the most energetically favorable bonding geometry