@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{56074,
  abstract     = {{Effective photoinduced charge transfer makes molecular bimetallic assemblies attractive for applications as active light‐induced proton reduction systems. Developing competitive base metal dyads is mandatory for a more sustainable future. However, the electron transfer mechanisms from the photosensitizer to the proton reduction catalyst in base metal dyads remain so far unexplored. A Fe─Co dyad that exhibits photocatalytic H2 production activity is studied using femtosecond X‐ray emission spectroscopy, complemented by ultrafast optical spectroscopy and theoretical time‐dependent DFT calculations, to understand the electronic and structural dynamics after photoexcitation and during the subsequent charge transfer process from the Fe(II) photosensitizer to the cobaloxime catalyst. This novel approach enables the simultaneous measurement of the transient X‐ray emission at the iron and cobalt K‐edges in a two‐color experiment. With this methodology, the excited state dynamics are correlated to the electron transfer processes, and evidence of the Fe→Co electron transfer as an initial step of proton reduction activity is unraveled.}},
  author       = {{Nowakowski, Michał and Huber‐Gedert, Marina and Elgabarty, Hossam and Kalinko, Aleksandr and Kubicki, Jacek and Kertmen, Ahmet and Lindner, Natalia and Khakhulin, Dmitry and Lima, Frederico A. and Choi, Tae‐Kyu and Biednov, Mykola and Schmitz, Lennart and Piergies, Natalia and Zalden, Peter and Kubicek, Katerina and Rodriguez‐Fernandez, Angel and Salem, Mohammad Alaraby and Canton, Sophie E. and Bressler, Christian and Kühne, Thomas D. and Gawelda, Wojciech and Bauer, Matthias}},
  issn         = {{2198-3844}},
  journal      = {{Advanced Science}},
  keywords     = {{Photo, Xray}},
  publisher    = {{Wiley}},
  title        = {{{Ultrafast Two‐Color X‐Ray Emission Spectroscopy Reveals Excited State Landscape in a Base Metal Dyad}}},
  doi          = {{10.1002/advs.202404348}},
  year         = {{2024}},
}

@article{49608,
  abstract     = {{<jats:p>The effects of backbone amine functionalization in three new homoleptic C^N^C type ruthenium(II) complexes bearing a tridentate bis‐imidazole‐2‐ylidene pyridine ligand framework are characterized and studied by single crystal diffraction, electrochemistry, optical spectroscopy and transient absorption spectroscopy in combination with ab initio DFT calculations. Functionalization by dimethylamine groups in 4‐position of the pyridine backbone significantly influences the properties of the complexes as revealed by comparison with the unfunctionalized references. As a result of the amine functionalization, a higher molar absorption coefficient of the MLCT bands, a decreased photoluminescence quantum yield at room temperature together with a shortened excited state lifetime but an improved photostability is observed. Introduction of electron donating and withdrawing groups at the NHC unit modifies the electronic and optical properties, such as the oxidation potential, absorption and emission properties, and the lifetimes of the excited states.</jats:p>}},
  author       = {{Fritsch, Lorena and Vukadinovic, Yannik and Lang, Moritz and Naumann, Robert and Bertrams, Maria-Sophie and Kruse, Ayla and Schoch, Roland and Müller, Patrick and Neuba, Adam and Dierks, Philipp and Lochbrunner, Stefan and Kerzig, Christoph and Heinze, Katja and Bauer, Matthias}},
  issn         = {{2367-0932}},
  journal      = {{ChemPhotoChem}},
  keywords     = {{Photo}},
  publisher    = {{Wiley}},
  title        = {{{Chemical and photophysical properties of amine functionalized bis‐NHC‐pyridine‐Ru(II) complexes}}},
  doi          = {{10.1002/cptc.202300281}},
  year         = {{2023}},
}

@article{46548,
  abstract     = {{<jats:p>The use of iron as a replacement for noble metals in photochemical and photophysical applications is challenging due to the typically fast deactivation of short-lived catalytically active states. Recent success of a cyclometalated iron(III) complex utilizing a bis-tridentate ligand motif inspired the use of phenyl-1H-pyrazole as a bidentate ligand. Five complexes using the tris(1-phenylpyrazolato-N,C2)iron(III) complex scaffold are presented. In addition to the parent complex, four derivatives with functionalization in the meta-position of the phenyl ring are thoroughly investigated by single crystal diffractometry, UV-Vis-spectroscopy, and cyclic voltammetry. Advanced X-ray spectroscopy in the form of X-ray absorption and emission spectroscopy allows unique insights into the electronic structure as well as DFT calculations. The ligand design leads to overlapping MLCT and LMCT absorption bands, and emissive behavior is suppressed by low-lying MC states.</jats:p>}},
  author       = {{Hirschhausen, Tanja and Fritsch, Lorena and Lux, Franziska and Steube, Jakob and Schoch, Roland and Neuba, Adam and Egold, Hans and Bauer, Matthias}},
  issn         = {{2304-6740}},
  journal      = {{Inorganics}},
  keywords     = {{Photo}},
  number       = {{7}},
  publisher    = {{MDPI AG}},
  title        = {{{Iron(III)-Complexes with N-Phenylpyrazole-Based Ligands}}},
  doi          = {{10.3390/inorganics11070282}},
  volume       = {{11}},
  year         = {{2023}},
}