@article{60600, abstract = {{In the search for noble metal free photocatalytic systems, iron is the dream candidate. To increase excited state lifetimes of iron complexes, the multichromophoric approach is promising, combining organic chromophores with photoactive iron complexes, potentially enabling a reservoir effect. We present a series of chromophore-functionalized complexes based on the parental FeIII complex [Fe(ImP)2][PF6] (HImP = 1,1′-(1,3-phenylene)bis(3-methyl-1-imidazole-2-ylidene)). The four organic chromophores benzene, naphthalene, anthracene, and pyrene are attached to the ImP-ligand in para-position to the coordination site to systematically investigate the influence of the steric demand and electronic properties of the chromophore on charge transfer lifetimes as well as photodynamics. A thorough ground state characterization was conducted in addition to investigations of the excited state dynamics by transient absorption spectroscopy and streak camera emission measurements. The conclusions drawn are supported by extensive DFT calculations. The emission coefficients could be significantly improved by the addition of chromophores. After excitation of the complexes with larger chromophores, coplanarization of the backbone and complex motif occurs to stabilize the formal charge. This results in population of a superligand state that exhibits a much faster radiationless relaxation to the ground state compared to the parent complex, hindering a reservoir effect.}}, author = {{Schmitz, Lennart and Argüello Cordero, Miguel A. and Al-Marri, Mohammed J. and Schoch, Roland and Egold, Hans and Neuba, Adam and Steube, Jakob and Bracht, Bastian Johannes and Bokareva, Olga S. and Lochbrunner, Stefan and Bauer, Matthias}}, issn = {{0020-1669}}, journal = {{Inorganic Chemistry}}, keywords = {{Photo}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Chromophore Induced Effects in Iron(III) Complexes}}}, doi = {{10.1021/acs.inorgchem.5c00526}}, year = {{2025}}, } @article{58180, abstract = {{A series of CoIII complexes [Co(RImP)2][PF6], with HMeImP = 1,1′-(1,3-phenylene)bis(3-methyl-1-imidazole-2-ylidene)) and R = Me, Et, iPr, nBu, is presented in this work. The influence of the strong donor ligand on the ground and excited-state photophysical properties was investigated in the context of different alkyl substituents at the imidazole nitrogen. X-ray diffraction revealed no significant alterations of the structures and all differences in the series emerge from the electronic structures. These were probed via cyclic voltammetry and UV–vis spectroscopy, detailing the influence of the different alkyl substituents on the ground-state properties. All complexes are emissive at 77 K from a 3MC state, which exhibits lifetimes in the range of 1–5 ns at room temperature, depending on the alkyl substituent. Therefore, it is clearly shown that even small differences in the electronic structure have a large impact on the details of the excited state landscape. The observed behavior was rationalized by a detailed DFT analysis, which shows that the minimum-energy crossing point to the ground-state is located only slightly above the MC energy: Consequently, nonradiative decay to the ground state at room temperature is enabled, while at 77 K this path is prohibited, leading to low-temperature 3MC emission.}}, author = {{Krishna, Athul and Fritsch, Lorena and Steube, Jakob and Argüello Cordero, Miguel A. and Schoch, Roland and Neuba, Adam and Lochbrunner, Stefan and Bauer, Matthias}}, issn = {{0020-1669}}, journal = {{Inorganic Chemistry}}, keywords = {{Photo}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Low Temperature Emissive Cyclometalated Cobalt(III) Complexes}}}, doi = {{10.1021/acs.inorgchem.4c04479}}, year = {{2025}}, } @article{56075, abstract = {{An isostructural series of FeII, FeIII, and Fe(IV)complexes [Fe(ImP)2]0/+/2+ utilizing the ImP 1,1′-(1,3-phenylene)-bis(3-methyl-1-imidazol-2-ylidene) ligand, combining N-heterocy-clic carbenes and cyclometalating functions, is presented. The strong donor motif stabilizes the high-valent Fe(IV) oxidation state yet keeps the FeII oxidation state accessible from the parent Fe(III)compound. Chemical oxidation of [Fe(ImP)2]+ yields stable [FeIV(ImP)2]2+. In contrast, [FeII(ImP)2]0, obtained by reduction,is highly sensitive toward oxygen. Exhaustive ground state characterization by single-crystal X-ray diffraction, 1H NMR,Mössbauer spectroscopy, temperature-dependent magnetic measurements, a combination of X-ray absorption near edge structureand valence-to-core, as well as core-to-core X-ray emission spectroscopy, complemented by detailed density functional theory (DFT) analysis, reveals that the three complexes[Fe(ImP)2]0/+/2+ can be unequivocally attributed to low-spin d6, d5, and d4 complexes. The excited state landscape of the Fe(II) and Fe(IV) complexes is characterized by short-lived 3MLCT and 3LMCT states, with lifetimes of 5.1 and 1.4 ps, respectively. In the FeII-compound, an energetically low-lying MC state leads to fast deactivation of the MLCT state. The distorted square-pyramidal state, where one carbene is dissociated, can not only relax into the ground state, but also into a singlet dissociated state. Its formation was investigated with time-dependent optical spectroscopy, while insights into its structure were gained by NMR spectroscopy.}}, author = {{Steube, Jakob and Fritsch, Lorena and Kruse, Ayla and Bokareva, Olga S. and Demeshko, Serhiy and Elgabarty, Hossam and Schoch, Roland and Alaraby, Mohammad and Egold, Hans and Bracht, Bastian Johannes and Schmitz, Lennart and Hohloch, Stephan and Kühne, Thomas D. and Meyer, Franc and Kühn, Oliver and Lochbrunner, Stefan and Bauer, Matthias}}, issn = {{0020-1669}}, journal = {{Inorganic Chemistry}}, keywords = {{Photo}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Isostructural Series of a Cyclometalated Iron Complex in Three Oxidation States}}}, doi = {{10.1021/acs.inorgchem.4c02576}}, year = {{2024}}, } @article{52345, abstract = {{Photoactive chromium(III) complexes saw a conceptual breakthrough with the discovery of the prototypical molecular ruby mer-[Cr(ddpd)2]3+ (ddpd = N,N′-dimethyl-N,N′-dipyridin-2-ylpyridine-2,6-diamine), which shows intense long-lived near-infrared (NIR) phosphorescence from metal-centered spin-flip states. In contrast to the numerous studies on chromium(III) photophysics, only 10 luminescent molybdenum(III) complexes have been reported so far. Here, we present the synthesis and characterization of mer-MoX3(ddpd) (1, X = Cl; 2, X = Br) and cisfac-[Mo(ddpd)2]3+ (cisfac-[3]3+), an isomeric heavy homologue of the prototypical molecular ruby. For cisfac-[3]3+, we found strong zero-field splitting using magnetic susceptibility measurements and electron paramagnetic resonance spectroscopy. Electronic spectra covering the spin-forbidden transitions show that the spin-flip states in mer-1, mer-2, and cisfac-[3]3+ are much lower in energy than those in comparable chromium(III) compounds. While all three complexes show weak spin-flip phosphorescence in NIR-II, the emission of cisfac-[3]3+ peaking at 1550 nm is particularly low in energy. Femtosecond transient absorption spectroscopy reveals a short excited-state lifetime of 1.4 ns, 6 orders of magnitude shorter than that of mer-[Cr(ddpd)2]3+. Using density functional theory and ab initio multireference calculations, we break down the reasons for this disparity and derive principles for the design of future stable photoactive molybdenum(III) complexes.}}, author = {{Kitzmann, Winald R. and Hunger, David and Reponen, Antti-Pekka M. and Förster, Christoph and Schoch, Roland and Bauer, Matthias and Feldmann, Sascha and van Slageren, Joris and Heinze, Katja}}, issn = {{0020-1669}}, journal = {{Inorganic Chemistry}}, keywords = {{Inorganic Chemistry, Physical and Theoretical Chemistry}}, number = {{39}}, pages = {{15797--15808}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Electronic Structure and Excited-State Dynamics of the NIR-II Emissive Molybdenum(III) Analogue to the Molecular Ruby}}}, doi = {{10.1021/acs.inorgchem.3c02186}}, volume = {{62}}, year = {{2023}}, } @article{62854, abstract = {{Highly selective rare-earth separation has become increasingly important due to the indispensable role of these elements in various cutting-edge technologies including clean energy. However, the similar physicochemical properties of rare-earth elements (REEs) render their separation very challenging, and the development of new selective receptors for these elements is potentially of very considerable economic and environmental importance. Herein, we report the development of a series of 4-phosphoryl pyrazolone receptors for the selective separation of trivalent lanthanum, europium, and ytterbium as the representatives of light, middle, and heavy REEs, respectively. X-ray crystallography studies were employed to obtain solid-state structures across 11 of the resulting complexes, allowing comparative structure–function relationships to be probed, including the effect of lanthanide contraction that occurs along the series from lanthanum to europium to ytterbium and which potentially provides a basis for REE ion separation. In addition, the influence of ligand structure and lipophilicity on lanthanide binding and selectivity was systematically investigated via n-octanol/water distribution and liquid–liquid extraction (LLE) studies. Corresponding stoichiometry relationships between solid and solution states were well established using slope analyses. The results provide new insights into some fundamental lanthanide coordination chemistry from a separation perspective and establish 4-phosphoryl pyrazolone derivatives as potential practical extraction reagents for the selective separation of REEs in the future.}}, author = {{Zhang, Jianfeng and Wenzel, Marco and Schnaars, Kathleen and Hennersdorf, Felix and Lindoy, Leonard F. and Weigand, Jan J.}}, issn = {{0020-1669}}, journal = {{Inorganic Chemistry}}, number = {{7}}, pages = {{3212--3228}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Highly Tunable 4-Phosphoryl Pyrazolone Receptors for Selective Rare-Earth Separation}}}, doi = {{10.1021/acs.inorgchem.2c04221}}, volume = {{62}}, year = {{2023}}, } @article{41012, abstract = {{Here we explore the electronic structure of the diiron complex [(dppf)Fe(CO)3]0/+ [10/+; dppf = 1,1′-bis(diphenylphosphino)ferrocene] in two oxidation states by an advanced multitechnique experimental approach. A combination of magnetic circular dichroism, X-ray absorption and emission, high-frequency electron paramagnetic resonance (EPR), and Mössbauer spectroscopies is used to establish that oxidation of 10 occurs on the carbonyl iron ion, resulting in a low-spin iron(I) ion. It is shown that an unequivocal result is obtained by combining several methods. Compound 1+ displays slow spin dynamics, which is used here to study its geometric structure by means of pulsed EPR methods. Surprisingly, these data show an association of the tetrakis[3,5-bis(trifluoromethylphenyl)]borate counterion with 1+.}}, author = {{Winkler, Mario and Schnierle, Marc and Ehrlich, Felix and Mehnert, Kim-Isabelle and Hunger, David and Sheveleva, Alena M. and Burkhardt, Lukas and Bauer, Matthias and Tuna, Floriana and Ringenberg, Mark R. and van Slageren, Joris}}, issn = {{0020-1669}}, journal = {{Inorganic Chemistry}}, keywords = {{Inorganic Chemistry, Physical and Theoretical Chemistry}}, number = {{5}}, pages = {{2856--2865}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Electronic Structure of a Diiron Complex: A Multitechnique Experimental Study of [(dppf)Fe(CO) 3]+/0}}}, doi = {{10.1021/acs.inorgchem.0c03259}}, volume = {{60}}, year = {{2021}}, } @article{62851, abstract = {{To reduce high-level radiotoxic waste generated by nuclear power plants, highly selective separation agents for minor actinides are mandatory. The mixed N,O-donor ligand N,N,N′,N′-tetrakis[(6-carboxypyridin-2-yl)methyl]ethylenediamine (H4TPAEN; 1) has shown good performance as a masking agent in Am3+/Eu3+ separation studies. Adjustments on the pyridyl backbone to raise the hydrophilicity led to a decrease in selectivity and a decrease in M3+–Nam interactions. An enhanced basicity of the pyridyl N-donors was given as a cause. In this work, we examine whether a decrease in O-donor basicity can promote the M3+–Nam interactions. Therefore, we replace the deprotonated “charged” carboxylic acid groups of TPAEN4– by neutral amide groups and introduce N,N,N′,N’-tetrakis[(6-N″,N′′-diethylcarbamoylpyridin-2-yl)methyl]ethylenediamine (TPAMEN; 2) as a new ligand. TPAMEN was crystallized with Eu(OTf)3 and Eu(NO3)3·6H2O to form positively charged 1:1 [Eu(TPAMEN)]3+ complexes in the solid state. Alterations in the M–O/N bond distances are compared to [Eu(TPAEN)]− and investigated by DFT calculations to expose the differences in charge/energy density distributions at europium(III) and the donor functionalities of the TPAEN4– and TPAMEN. On the basis of estimations of the bond orders, atomic charges spin populations, and density of states in the Eu and potential Am and Cm complexes, the specific contributions of the donor–metal interaction are analyzed. The prediction of complex formation energy differences for the [M(TPAEN)]− and [M(TPAMEN)]3+ (M3+ = Eu3+, Am3+) complexes provide an outlook on the potential performance of TPAMEN in Am3+/Eu3+ separation.}}, author = {{Schnaars, Kathleen and Kaneko, Masashi and Fujisawa, Kiyoshi}}, issn = {{0020-1669}}, journal = {{Inorganic Chemistry}}, number = {{4}}, pages = {{2477--2491}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Effect of Oxygen-Donor Charge on Adjacent Nitrogen-Donor Interactions in Eu3+ Complexes of Mixed N,O-Donor Ligands Demonstrated on a 10-Fold [Eu(TPAMEN)]3+ Chelate Complex}}}, doi = {{10.1021/acs.inorgchem.0c03405}}, volume = {{60}}, year = {{2021}}, } @article{18534, author = {{Vukadinovic, Yannik and Burkhardt, Lukas and Päpcke, Ayla and Miletic, Anabel and Fritsch, Lorena and Altenburger, Björn and Schoch, Roland and Neuba, Adam and Lochbrunner, Stefan and Bauer, Matthias}}, issn = {{0020-1669}}, journal = {{Inorganic Chemistry}}, pages = {{8762--8774}}, title = {{{When Donors Turn into Acceptors: Ground and Excited State Properties of FeII Complexes with Amine-Substituted Tridentate Bis-imidazole-2-ylidene Pyridine Ligands}}}, doi = {{10.1021/acs.inorgchem.0c00393}}, year = {{2020}}, } @article{46546, author = {{Vukadinovic, Yannik and Burkhardt, Lukas and Päpcke, Ayla and Miletic, Anabel and Fritsch, Lorena and Altenburger, Björn and Schoch, Roland and Neuba, Adam and Lochbrunner, Stefan and Bauer, Matthias}}, issn = {{0020-1669}}, journal = {{Inorganic Chemistry}}, keywords = {{Inorganic Chemistry, Physical and Theoretical Chemistry}}, number = {{13}}, pages = {{8762--8774}}, publisher = {{American Chemical Society (ACS)}}, title = {{{When Donors Turn into Acceptors: Ground and Excited State Properties of FeII Complexes with Amine-Substituted Tridentate Bis-imidazole-2-ylidene Pyridine Ligands}}}, doi = {{10.1021/acs.inorgchem.0c00393}}, volume = {{59}}, year = {{2020}}, } @article{16311, author = {{Burkhardt, Lukas and Vukadinovic, Yannik and Nowakowski, Michał and Kalinko, Aleksandr and Rudolph, Julian and Carlsson, Per-Anders and Jacob, Christoph R. and Bauer, Matthias}}, issn = {{0020-1669}}, journal = {{Inorganic Chemistry}}, pages = {{3551--3561}}, title = {{{Electronic Structure of the Hieber Anion [Fe(CO)3(NO)]− Revisited by X-ray Emission and Absorption Spectroscopy}}}, doi = {{10.1021/acs.inorgchem.9b02092}}, year = {{2020}}, } @article{41018, author = {{Dierks, Philipp and Päpcke, Ayla and Bokareva, Olga S. and Altenburger, Björn and Reuter, Thomas and Heinze, Katja and Kühn, Oliver and Lochbrunner, Stefan and Bauer, Matthias}}, issn = {{0020-1669}}, journal = {{Inorganic Chemistry}}, keywords = {{Inorganic Chemistry, Physical and Theoretical Chemistry}}, number = {{20}}, pages = {{14746--14761}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Ground- and Excited-State Properties of Iron(II) Complexes Linked to Organic Chromophores}}}, doi = {{10.1021/acs.inorgchem.0c02039}}, volume = {{59}}, year = {{2020}}, } @article{41019, author = {{Zobel, J. Patrick and Bokareva, Olga S. and Zimmer, Peter and Wölper, Christoph and Bauer, Matthias and González, Leticia}}, issn = {{0020-1669}}, journal = {{Inorganic Chemistry}}, keywords = {{Inorganic Chemistry, Physical and Theoretical Chemistry}}, number = {{20}}, pages = {{14666--14678}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Intersystem Crossing and Triplet Dynamics in an Iron(II) N-Heterocyclic Carbene Photosensitizer}}}, doi = {{10.1021/acs.inorgchem.0c02147}}, volume = {{59}}, year = {{2020}}, } @article{41330, author = {{Burkhardt, Lukas and Vukadinovic, Yannik and Nowakowski, Michał and Kalinko, Aleksandr and Rudolph, Julian and Carlsson, Per-Anders and Jacob, Christoph R. and Bauer, Matthias}}, issn = {{0020-1669}}, journal = {{Inorganic Chemistry}}, keywords = {{Inorganic Chemistry, Physical and Theoretical Chemistry}}, number = {{6}}, pages = {{3551--3561}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Electronic Structure of the Hieber Anion [Fe(CO)3(NO)]− Revisited by X-ray Emission and Absorption Spectroscopy}}}, doi = {{10.1021/acs.inorgchem.9b02092}}, volume = {{59}}, year = {{2020}}, } @article{16313, author = {{Burkhardt, Lukas and Mueller, Carsten and Groß, Oliver A. and Sun, Yu and Sitzmann, Helmut and Bauer, Matthias}}, issn = {{0020-1669}}, journal = {{Inorganic Chemistry}}, pages = {{6609--6618}}, title = {{{The Bonding Situation in the Dinuclear Tetra-Hydrido Complex [{5CpFe}2(μ-H)4] Revisited by Hard X-Ray Spectroscopy}}}, doi = {{10.1021/acs.inorgchem.8b03032}}, year = {{2018}}, } @article{41039, author = {{Burkhardt, Lukas and Mueller, Carsten and Groß, Oliver A. and Sun, Yu and Sitzmann, Helmut and Bauer, Matthias}}, issn = {{0020-1669}}, journal = {{Inorganic Chemistry}}, keywords = {{Inorganic Chemistry, Physical and Theoretical Chemistry}}, number = {{10}}, pages = {{6609--6618}}, publisher = {{American Chemical Society (ACS)}}, title = {{{The Bonding Situation in the Dinuclear Tetra-Hydrido Complex [{5CpFe}2(μ-H)4] Revisited by Hard X-Ray Spectroscopy}}}, doi = {{10.1021/acs.inorgchem.8b03032}}, volume = {{58}}, year = {{2018}}, } @article{16318, author = {{Burkhardt, Lukas and Holzwarth, Michael and Plietker, Bernd and Bauer, Matthias}}, issn = {{0020-1669}}, journal = {{Inorganic Chemistry}}, pages = {{13300--13310}}, title = {{{Detection and Characterization of Hydride Ligands in Iron Complexes by High-Resolution Hard X-ray Spectroscopy and Implications for Catalytic Processes}}}, doi = {{10.1021/acs.inorgchem.7b02063}}, year = {{2017}}, } @article{16317, author = {{Zimmer, Peter and Burkhardt, Lukas and Friedrich, Aleksej and Steube, Jakob and Neuba, Adam and Schepper, Rahel and Müller, Patrick and Flörke, Ulrich and Huber, Marina and Lochbrunner, Stefan and Bauer, Matthias}}, issn = {{0020-1669}}, journal = {{Inorganic Chemistry}}, pages = {{360--373}}, title = {{{The Connection between NHC Ligand Count and Photophysical Properties in Fe(II) Photosensitizers: An Experimental Study}}}, doi = {{10.1021/acs.inorgchem.7b02624}}, year = {{2017}}, } @article{16323, author = {{Vollmers, Nora Jenny and Müller, Patrick and Hoffmann, Alexander and Herres-Pawlis, Sonja and Rohrmüller, Martin and Schmidt, Wolf Gero and Gerstmann, Uwe and Bauer, Matthias}}, issn = {{0020-1669}}, journal = {{Inorganic Chemistry}}, pages = {{11694--11706}}, title = {{{Experimental and Theoretical High-Energy-Resolution X-ray Absorption Spectroscopy: Implications for the Investigation of the Entatic State}}}, doi = {{10.1021/acs.inorgchem.6b01704}}, year = {{2016}}, } @article{13476, author = {{Vollmers, Nora Jenny and Müller, Patrick and Hoffmann, Alexander and Herres-Pawlis, Sonja and Rohrmüller, Martin and Schmidt, Wolf Gero and Gerstmann, Uwe and Bauer, Matthias}}, issn = {{0020-1669}}, journal = {{Inorganic Chemistry}}, pages = {{11694--11706}}, title = {{{Experimental and Theoretical High-Energy-Resolution X-ray Absorption Spectroscopy: Implications for the Investigation of the Entatic State}}}, doi = {{10.1021/acs.inorgchem.6b01704}}, volume = {{55}}, year = {{2016}}, } @article{41228, author = {{Bräunlich, Irene and Sánchez-Ferrer, Antoni and Bauer, Matthias and Schepper, Rahel and Knüsel, Philippe and Dshemuchadse, Julia and Mezzenga, Raffaele and Caseri, Walter}}, issn = {{0020-1669}}, journal = {{Inorganic Chemistry}}, keywords = {{Inorganic Chemistry, Physical and Theoretical Chemistry}}, number = {{7}}, pages = {{3546--3557}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Polynuclear Iron(II)–Aminotriazole Spincrossover Complexes (Polymers) In Solution}}}, doi = {{10.1021/ic403035u}}, volume = {{53}}, year = {{2014}}, }