Dieter Sorsche
@uni-ulm.de
Habilitation, Institut für Anorganische Chemie 1
Universität Ulm
RESEARCH, TEACHING, or OTHER INTERESTS
Chemistry, Inorganic Chemistry, Spectroscopy, Catalysis
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Marius Müßler, Andrea Pannwitz, and Dieter Sorsche
Wiley
Abstract„Nur während der ruhigen Zeit zwischen den Jahren, wenn niemand im Labor ist, können die Kristalle schön wachsen“, heißt es, oder „Bestimmte Kristalle wachsen nur im Winter im dunklen, kalten Kühlschrank“. Manche verlassen sich auf Fliegenbeine als Kristallisationskeime oder stellen Kristallansätze offen auf die Fensterbank. Tipps und Tricks, um Kristalle herzustellen.
Stefan Repp, Moritz Remmers, Alexandra Stefanie Jessica Rein, Dieter Sorsche, Dandan Gao, Montaha Anjass, Mihail Mondeshki, Luca M. Carrella, Eva Rentschler, and Carsten Streb
Springer Science and Business Media LLC
AbstractThe introduction of metal sites into molecular metal oxides, so-called polyoxometalates, is key for tuning their structure and reactivity. The complex mechanisms which govern metal-functionalization of polyoxometalates are still poorly understood. Here, we report a coupled set of light-dependent and light-independent reaction equilibria controlling the mono- and di-metal-functionalization of a prototype molecular vanadium oxide cluster. Comprehensive mechanistic analyses show that coordination of a Mg2+ ion to the species {(NMe2H2)2[VV12O32Cl]}3- results in formation of the mono-functionalized {(NMe2H2)[(MgCl)VV12O32Cl]}3- with simultaneous release of a NMe2H2+ placeholder cation. Irradiation of this species with visible light results in one-electron reduction of the vanadate, exchange of the second NMe2H2+ with Mg2+, and formation/crystallization of the di-metal-functionalized [(MgCl)2VIVVV11O32Cl]4-. Mechanistic studies show how stimuli such as light or competing cations affect the coupled equilibria. Transfer of this synthetic concept to other metal cations is also demonstrated, highlighting the versatility of the approach.
Andrea Pannwitz and Dieter Sorsche
Wiley
AbstractPhotochemische Prozesse finden in Synthese, Oleds und katalytischen Prozessen statt. 3d‐Übergangsmetalle wie Eisen können die Farbstoffe und Photosensibilisatoren aus Schwermetallen ablösen.
Orion Staples, Magali S. Ferrandon, Guillaume P. Laurent, Uddhav Kanbur, A. Jeremy Kropf, Michael R. Gau, Patrick J. Carroll, Katherine McCullough, Dieter Sorsche, Frédéric A. Perras,et al.
American Chemical Society (ACS)
Catalytic C-H borylation is an attractive method for the conversion of the most abundant hydrocarbon, methane (CH4), to a mild nucleophilic building block. However, existing CH4 borylation catalysts often suffer from low turnover numbers and conversions, which is hypothesized to result from inactive metal hydride agglomerates. Herein we report that the heterogenization of a bisphosphine molecular precatalyst, [(dmpe)Ir(cod)CH3], onto amorphous silica dramatically enhances its performance, yielding a catalyst that is 12-times more efficient than the current standard for CH4 borylation. The catalyst affords over 2000 turnovers at 150 °C in 16 h with a selectivity of 91.5% for mono- vs diborylation. Higher catalyst loadings improve yield and selectivity for the monoborylated product (H3CBpin) with 82.8% yield and >99% selectivity being achieved with 1255 turnovers. X-ray absorption and dynamic nuclear polarization-enhanced solid-state NMR spectroscopic studies identify the supported precatalyst as an IrI species, and indicate that upon completion of catalysis, multinuclear Ir polyhydrides are not formed. This is consistent with the hypothesis that immobilization of the organometallic Ir species on a surface prevents bimolecular decomposition pathways. Immobilization of the homogeneous IrI fragment onto amorphous silica represents a unique and simple strategy to improve the TON and longevity of a CH4 borylation catalyst.
Sebastian Knoll, Matthias Hänle, Alexander K. Mengele, Dieter Sorsche, Sven Rau, and Carsten Streb
Wiley
AbstractCLICK‐chemistry has become a universal route to covalently link organic molecules functionalized with azides and alkynes, respectively. Here, we report how CLICK‐chemistry can be used to attach oligoaromatic organic moieties to Dawson‐type polyoxometalates. In step one, the lacunary Dawson anion [α2‐P2W17O61]6− is functionalized with phosphonate anchors featuring peripheral azide groups. In step two, this organic‐inorganic hybrid undergoes microwave‐assisted CLICK coupling. We demonstrate the versatility of this route to access a series of Dawson anions covalently functionalized with oligoaromatic groups. The supramolecular chemistry and aggregation of these systems in solution is explored, and we report distinct changes in charge‐transfer behavior depending on the size of the oligoaromatic π‐system.
Stefan Repp, Kim Lara Junginger, Dieter Sorsche, Theresa Zorn, Ann-Christin Pöppler, Yuji Kikukawa, Yoshihito Hayashi, and Carsten Streb
Royal Society of Chemistry (RSC)
Insights into the template-induced self-assembly of dodecanuclear polyoxovanadate host–guest complexes is provided by solution and solid-state methods.
Nicolas Meitinger, Subrata Mandal, Dieter Sorsche, Andrea Pannwitz, and Sven Rau
MDPI AG
Rhenium(I) complexes of type [Re(CO)3(NN)Cl] (NN = α-diimine) with MLCT absorption in the orange-red region of the visible spectrum have been synthesized and fully characterized, including single crystal X-ray diffraction on two complexes. The strong bathochromic shift of MLCT absorption was achieved through extension of the π-system of the electron-poor bidiazine ligand 4,4′-bipyrimidine by the addition of fused phenyl rings, resulting in 4,4′-biquinazoline. Furthermore, upon anionic cyclization of the twisted bidiazine, a new 4N-doped perylene ligand, namely, 1,3,10,12-tetraazaperylene, was obtained. Electrochemical characterization revealed a significant stabilization of the LUMO in this series, with the first reduction of the azaperylene found at E1/2(0/−) = −1.131 V vs. Fc+/Fc, which is the most anodic half-wave potential observed for N-doped perylene derivatives so far. The low LUMO energies were directly correlated to the photophysical properties of the respective complexes, resulting in a strongly red-shifted MLCT absorption band in chloroform with a λmax = 586 nm and high extinction coefficients (ε586nm > 5000 M−1 cm−1) ranging above 700 nm in the case of the tetraazaperylene complex. Such low-energy MLCT absorption is highly unusual for Re(I) α-diimine complexes, for which these bands are typically found in the near UV. The reported 1,3,10,12-tetraazaperylene complex displayed the [Re(CO)3(α-diimine)Cl] complex with the strongest MLCT red shift ever reported. UV–Vis NIR spectroelectrochemical investigations gave further insights into the nature and stability of the reduced states. The electron-poor ligands explored herein open up a new path for designing metal complexes with strongly red-shifted absorption, thus enabling photocatalysis and photomedical applications with low-energy, tissue-penetrating red light in future.
Meena Ghosh, Dieter Sorsche, Rezwana Binte Ahmed, and Montaha Anjass
Wiley
AbstractDecavanadate ([V10O28]6−, {V10}) clusters are a potential electrode material for lithium and post‐lithium batteries; however, their low stability due to the solubility in liquid organic electrolytes has been challenging. These molecular clusters are also prone to transform into solid‐state oxides at a moderate temperature needed in the typical electrode fabrication process. Hence, controlling the solubility and improving the thermal stability of compounds are essential to make them more viable options for use as battery electrodes. This study shows a crystal engineering approach to stabilize the cluster with organic guanidinium (Gdm+) cation through the hydrogen‐bonding interactions between the amino groups of the cation and the anion. The comparison of solubility and thermal stability of the Gdm{V10} with another cluster bearing tetrabutylammonium (Tba+) cation reveals the better stability of cation‐anion assembly in the former than the latter. As a result, the Gdm{V10} delivers better rate capability and cycling stability than Tba{V10} when tested as anode material in a half‐cell configuration of a sodium‐ion battery. Finally, the performance of the Gdm{V10} anode is also investigated in a lithium‐ion battery full cell with LiFePO4 cathode.
Stefan Repp, Michael Steiner, Montaha Anjass, Dieter Sorsche, and Carsten Streb
Royal Society of Chemistry (RSC)
The aggregation of supramolecular organic–inorganic 1D polymers is reported based on host–guest recognition between an organic macrocycle and an inorganic vanadium oxide cluster.
Ruihao Gong, Dariusz Mitoraj, Dandan Gao, Manuel Mundszinger, Dieter Sorsche, Ute Kaiser, Carsten Streb, Radim Beranek, and Sven Rau
Wiley
AbstractDue to their availability, low cost, nontoxicity, and tunability, polymeric carbon nitrides (CNx) represent one of the most attractive materials classes for the development of fully sustainable photo(electro)catalytic systems for solar‐driven water splitting. However, the development of CNx‐based photoanodes for visible light‐driven water oxidation to dioxygen is rather challenging, particularly due to issues related to photoelectrode stability and effective coupling of the light absorber with water oxidation catalysts. Herein, a triadic photoanode comprising a porous TiO2 electron collector scaffold sensitized by CNx coupled to a molecular cobalt polyoxometalate (CoPOM = [Co4(H2O)2(PW9O34)2]10) catalyst is reported. Complete water oxidation to dioxygen under visible (λ > 420 nm) light irradiation is demonstrated, with photocurrents down to relatively low bias potentials (0.2 V vs RHE). Furthermore, polyethyleneimine (PEI), a cationic polymer is shown to act as an effective and non‐sacrificial electrostatic linker for immobilization of the anionic CoPOM onto the negatively charged surface of CNx. The optimized deposition of CoPOM using the PEI linker translates directly into improved efficiency of the transfer of photogenerated holes to water molecules and to enhanced oxygen evolution. This work thus provides important design rules for effective immobilization of POM‐based catalysts into soft‐matter photoelectrocatalytic architectures for light‐driven water oxidation.
Ruihao Gong, Dandan Gao, Rongji Liu, Dieter Sorsche, Johannes Biskupek, Ute Kaiser, Sven Rau, and Carsten Streb
American Chemical Society (ACS)
J. Rolando Aguilar-Calderón, Dominik Fehn, Dieter Sorsche, Matthias Miehlich, Patrick J. Carroll, Ethan Zars, Karsten Meyer, and Daniel J. Mindiola
American Chemical Society (ACS)
Oxidation of the low-spin FeIV imido complex [{(tBupyrr)2py}Fe═NAd] (1) ((tBupyrr)2py2- = 2,6-bis(3,5-di-tert-butyl-pyrrolyl)pyridine, Ad = 1-adamantyl) with AgOAc or AgNO3 promotes reductive N-N bond coupling of the former imido nitrogen with a pyrrole nitrogen to form the respective ferric hydrazido-like pincer complexes [{(tBupyrrNAd)(tBupyrr)py}Fe(κ2-X)] (X = OAc-, 2OAc; NO3-, 2NO3). Reduction of 2OAc with KC8 cleaves the N-N bond to reform the FeIV imido ligand in 1, whereas acid-mediated demetalation of 2OAc or 2NO3 yields the free hydrazine ligand [(tBupyrrNHAd)(tBupyrrH)py] (3), the latter of which can be used as a direct entry to the iron imido complex when treated with [Fe{N(SiMe3)2}2]. In addition to characterizing these Fe systems, we show how this nitrene transfer strategy can be expanded to Co for the one-step synthesis of Co{(tBu-NHAdpyrr)(tBupyrr)py}] (4) ((tBu-NHAdpyrr)(tBupyrr)py2- = 2-(3-tBu-5-(1-adamantylmethyl-2-methylpropane-2-yl)-pyrrol-2-yl)-6-(3,5-tBu2-pyrrol-2-yl)-pyridine).
Dieter Sorsche, Matthias E. Miehlich, Keith Searles, Guillaume Gouget, Eva M. Zolnhofer, Skye Fortier, Chun-Hsing Chen, Michael Gau, Patrick J. Carroll, Christopher B. Murray,et al.
American Chemical Society (ACS)
A rare example of a dinuclear iron core with a non-linearly bridged dinitrogen ligand is reported in this work. One-electron reduction of [(tBupyrr2py)Fe(OEt2)] (1) (tBupyrr2py2- = 2,6-bis((3,5-di-tert-butyl)pyrrol-2-yl)pyridine) with KC8 yields the complex [K]2[(tBupyrr2py)Fe]2(μ2-η1:η1-N2) (2) where the unusual cis-divacant octahedral coordination geometry about each iron and the η5-cation-π coordination of two potassium ions with four pyrrolyl units of the ligand cause distortion of the bridging end-on μ-N2 about the FeN2Fe core. Attempts to generate an Et2O free version of 1 resulted instead in a dinuclear helical dimer [(tBupyrr2py)Fe]2 (3) via bridging of the pyridine moieties of the ligand. Reduction of 3 by two-electrons under N2 does not break up the dimer nor does it result in formation of 2, but instead formation of the ate-complex [K(OEt2)]2[(tBupyrr2py)Fe]2 (4). Reduction of 1 by two-electrons and in the presence of crown-ether forms the tetraanionic N2 complex [K2][K(18-crown-6)]2(tBupyrr2py)Fe]2(μ2-η1:η1-N2) (5), also having a distorted FeN2Fe moiety akin to 2. Complex 2 is thermally unstable and loses N2, disproportionating to Fe nanoparticles among other products. A combination of single-crystal X-ray diffraction studies, solution and solid state magnetic studies, and 57Fe Mössbauer spectroscopy have been applied to characterize complexes 2-5, whereas DFT studies have been used to help explain the bonding and electronic structure in these unique diiron-N2 complexes 2 and 5.
Pavel Zatsepin, Dieter Sorsche, Seihwan Ahn, Mu‐Hyun Baik, and Daniel J. Mindiola
Wiley
Seihwan Ahn, Dieter Sorsche, Simon Berritt, Michael R. Gau, Daniel J. Mindiola, and Mu-Hyun Baik
American Chemical Society (ACS)
Combined computational and experimental studies elucidate the mechanism and suggest rational design and optimization strategies of a bis(phosphine)-supported iridium-catalyst for methane monoborylation. The activation of the C–H bond in methane via oxidative addition using tris(boryl) iridium(III) complexes bearing bis-chelating supporting ligands is modeled computationally. This model shows that the use of the soft Lewis base ligand such as 1,2-bis(dimethylphosphino)ethane (dmpe) lowers the activation barrier of the rate-determining step as it facilitates polarization of the metal-center, lowering the barrier of the oxidative addition to afford a seven-coordinate iridium(V) intermediate. The experimental optimization of this reaction using high-throughput methods shows that up to 170 turnovers can be achieved at 150 °C (500 psi) within 16 h using bis(pinacolato)diboron, a well-defined homogeneous and monomeric catalyst (dmpe)Ir(COD)Cl that is readily available from commercial precursors, with selectivity...
Dieter Sorsche, Matthias E. Miehlich, Eva M. Zolnhofer, Patrick J. Carroll, Karsten Meyer, and Daniel J. Mindiola
American Chemical Society (ACS)
The reaction of elemental sulfur with the cis-divacant octahedral complex [(pyrr2py)Fe(OEt2)] (1; pyrr2py2- = 3,5-tBu2-bis(pyrrolyl)pyridine) yields the iron dimer [(pyrr-1-S-pyrrpy)Fe]2 (2; pyrr-1-S-pyrrpy2- = 3,5-(tBu2-pyrrolyl)(1-S-3,5-tBu2-pyrrolyl)pyridine) resulting from a pyrr2py2- ligand based S-oxidation of one pyrrole arm. Addition of the phosphorus ylide H2CPPh3 to 1 forms the ylide adduct [(pyrr2py)Fe(CH2PPh3)] (3), which upon reaction with elemental sulfur produces a rare example of a sulfurmethylenephosphorane adduct, [(pyrr2py)Fe(SCH2PPh3)] (4). The sulfur-oxidized pyrrole group of the ligand pyrr-1-S-pyrrpy2- can be reversed, since complex 2 exhibits S atom transferability via the addition of 2 equiv of H2CPPh3 to yield a mixture of compounds 3 and 4. For all complexes reported, the ferrous ion remains S = 2. Complexes 2-4 were characterized by single-crystal X-ray diffraction as well as 1H NMR spectroscopy, solid and solution magnetic studies, and 57Fe Mössbauer spectroscopic measurements.
Anne Stumper, Martin Lämmle, Alexander K. Mengele, Dieter Sorsche, and Sven Rau
Wiley
The applicability of RuII polypyridyl complexes with appropriate functionalities as substrates for biorthogonal coupling reactions is investigated. In detail, copper(I)‐catalyzed azide–alkyne cycloadditions (CuAAC), strain‐promoted azide–alkyne cycloadditions (SPAAC), and maleimide–thiol coupling reactions of ruthenium complexes are examined. The first examples of SPAAC in which the organic azide is provided by the metal complex are presented. All of the chromophores belong to one easy‐to‐synthesize scaffold, which has proven to be convenient for the application of metal chromophores. The fundamental photophysical properties of the examined compounds do not change with substitution, which is important for the design of chromophore conjugates. Furthermore, the limitations of CuAAC reactions will be discussed with regard to copper impurities in the products formed.
Sebastian A. Rommel, Dieter Sorsche, Maximilian Fleischmann, and Sven Rau
Wiley
AbstractPhosphorescent metal complexes with peripheral N‐H donor functionalities have attracted great attention as potential molecular sensing units for anionic species lately. In this contribution we discuss the development and potential of anion recognition and sensing features of recent examples of luminescent 2,2′‐biimidazole complexes of ruthenium(II), iridium(III), osmium(II) and cobalt(III). The general dependency of photophysical features in these complexes regarding the acid‐base chemistry of the peripheral N‐H functionalities will be outlined as a basic requirement for optical ion recognition. Systematic strategies for the tuning and specific improvement by synthetic means will be discussed regarding recent reports. With respect to their distinct photophysical features, different transition metals are considered individually to demonstrate particular trends regarding ligand modification within the respective groups. In summary, this review elucidates the current state‐of‐the‐art and future potential of the versatile class of 2,2′‐biimidazole based sensor chromophores.
Simon Kaufhold, Lydia Petermann, Dieter Sorsche, and Sven Rau
Wiley
The problematic consequences of using silver carbene precursors for the synthesis of NHC-complexes is elucidated with the example of dinuclear Ru-Rh/Ir photocatalysts. The presence of silver in the products is proven and an alternative silver-free synthetic approach successfully implemented. A significant difference in performance in photocatalytic hydrogen evolution reactions of catalysts generated by the different strategies is observed.
Anne Stumper, Thomas David Pilz, Markus Schaub, Helmar Görls, Dieter Sorsche, Katrin Peuntinger, Dirk Guldi, and Sven Rau
Wiley
Abstract: Providing bromo functionalized precursor molecules is essential to generate desired target compounds utilizing cross coupling reactions. Here we show an improved synthetic route - feasible at low temperatures and affording high yields - for the ligands 5-bromo-1,10-phenanthroline (1) and 5,6-dibromo-1,10-phenanthroline (2). Corresponding Ruthenium complexes providing 2 in varying numbers are easily accessible in high yields and the analogue to trishomoleptic [Ru(bpy)3]2+ (bpy= 2,2'-bipyridine), [Ru(2)3]2+, is presented. Comparison of the X-ray diffraction analyses provides detailed information about the structures of the ligands and their metal complexes. The investigation of electrochemical properties generated detailed information about the 3MLCT state localized on 2. We show conversion of heteroleptic Ruthenium complexes of these ligands in Suzuki cross coupling reactions whereas the ligands did not undergo Suzuki coupling under the used conditions.
S. Schönweiz, D. Sorsche, B. Schwarz, S. Rau, and C. Streb
Royal Society of Chemistry (RSC)
Synthesis, single-crystal X-ray diffraction structures and reactivity information is reported for covalently linked photoactive metal complex – polyoxometalate aggregates.
Johannes Habermehl, Dieter Sorsche, Petra Murszat, and Sven Rau
Wiley
Two synthetic approaches towards the mononuclear complex [(tbbpy)2OsII(tpphz)]2+ (tbbpy = 4,4′‐di‐tert‐butyl‐2,2′‐bipyridine; tpphz = tetrapyrido[3,2‐a:2′,3′‐c:3′′,2′′‐h:2′′′,3′′′‐j]phenazine) based on the precursor [(tbbpy)2OsIICl2] and its oxidized side product [(tbbpy)2OsIIICl2]+ are presented. The first route is analogous to that for the isostructural ruthenium complex, whereas the second strategy efficiently uses the oxidized OsIII complex under reducing conditions to obtain so‐called virtual dilution, which avoids the formation of the dinuclear complex [(tbbpy)2OsII(tpphz)OsII(tbbpy)2]. Concentration‐dependent NMR investigations were performed, and a dimerization constant (KD = 400) could be calculated due to π–π interactions of the tpphz moiety. Solid‐state structures of all synthesized complexes show comparable bond lengths and angles with respect to each other and their ruthenium analogues. Photophysical investigations show the expected absorption in the UV/Vis region and a single emission at 758 nm for [(tbbpy)2OsII(tpphz)]2+. Electrochemical measurements show comparable behavior to the structurally similar complexes [(bpy)2M(tpphz)]2+ (M = Os, Ru).
Lydia Petermann, Robert Staehle, Maxim Pfeifer, Christian Reichardt, Dieter Sorsche, Maria Wächtler, Jürgen Popp, Benjamin Dietzek, and Sven Rau
Wiley
Detailed investigations of a photocatalytic system capable of producing hydrogen under pre-catalytic aerobic conditions are reported. This system consists of the NHC precursor chromophore [Ru(tbbpy)2 (RR'ip)][PF6 ]3 (abbreviated as Ru(RR'ip)[PF6 ]3 ; tbbpy=4,4'-di-tert-butyl-2,2'-bipyridine, RR'ip=1,3-disubstituted-1H-imidazo[4,5-f][1,10]phenanthrolinium), the reduction catalyst Co(dmgH)2 (dmgH=dimethylglyoximato), and the electron donor ascorbic acid (AA). Screening studies with respect to solvent, cobaloxime catalyst, electron donor, pH, and concentrations of the individual components yielded optimized photocatalytic conditions. The system shows high activity based on Ru, with turnover numbers up to 2000 under oxygen-free and pre-catalytic aerobic conditions. The turnover frequency in the latter case was even higher than that for the oxygen-free catalyst system. The Ru complexes show high photostability and their first excited state is primarily located on the RR'ip ligand. X-ray crystallographic analysis of the rigid cyclophane-type ligand dd(ip)2 (Br)2 (dd(ip)2 =1,1',3,3'-bis(2,3,5,6-tetramethyl-1,4-phenylene)bis(methylene)bis(1H-imidazo[4,5-f][1,10]phenanthrolinium)) and the catalytic activity of its Ru complex [{(tbbpy)2 Ru}2 (μ-dd(ip)2 )][PF6 ]6 (abbreviated as Ru2 (dd(ip)2 )[PF6 ]6 ) suggest an intermolecular catalytic cycle.
Dieter Sorsche, Sebastian A. Rommel, and Sven Rau
Wiley
Three 2,2′-bibenzimidazole-bis(4,4′-di-tert-butyl-2,2′-bipyridine)ruthenium(II) complexes are presented and characterized with respect to their photophysical and structural properties. 4,4′,5,5′-Tetramethyl-2,2′-bibenzimidazole (L0), 4,4′-di(p-anisyl)-2,2′-bibenzimidazole (L1), and the ruthenium complexes K0 and K1 have been reported previously. The new complex K2 contains the structurally confined ligand 4,4′-di(o,o′-dimethyl-p-anisyl)-2,2′-bibenzimidazole. Owing to substitution at the 4,4′-positions of the bibenzimidazole ligands, complexes K1 and K2 have pincer-like geometries, as shown by 1H NMR spectroscopy and XRD studies. The emission intensities of these complexes are dimmed compared with that of K0, whereas titration experiments with tetrabutylammonium (TBA) salts of fluoride, chloride, bromide, and iodide show strongly enhanced sensitivity to hydrogen bonding with chloride and bromide ions, which increases the emission intensity to ca. 300 % of the original value, and they eventually outperform K0. With regard to the luminescence sensitivities, K1 and K2 set a new benchmark among 2,2′-biimidazole ruthenium(II) colorimetric halide sensors.
Dieter Sorsche, Markus Schaub, Frank W. Heinemann, Johannes Habermehl, Susanne Kuhri, Dirk Guldi, Julien Guthmuller, and Sven Rau
Royal Society of Chemistry (RSC)
Electrostatic repulsion between gold(iii) coordination spheres exceeds π-stacking for the first time in a tpphz-bridged dinuclear PMD model complex.