The structural, electronic, thermal and lattice thermal transport properties of the three hypothetical quaternary Heusler alloys FeRuTiX (X=Si, Ge, Sn) were investigated with the aid of first-principles calculations. All compounds were found to be semiconducting with a small indirect band gap. Flat bands near the conduction band edge and degenerate multi-bands near the valance band edge suggest that these systems should exhibit both large Seebeck coefficients and good electrical conductivity. The analysis of the calculated vibrational spectra showed that the three compounds are thermodynamically stable. The computed lattice thermal conductivity indicates that among the three compounds that of FeRuTiSn is rather low at high temperature. Indeed, a low lattice thermal conductivity (∼3.5 Wm−1 K−1 at 1000 K) together with a small electronic band gap (0.51 eV) with an appropriate electronic structure (disperse and flat bands) render FeRuTiSn a promising candidate as a high-temperature thermoelectric material.

The catalytic hydrogenation of nitroarenes using hydrogen gas as reducing agent to form substituted aniline derivates is an important reaction in industry and academic research. Here, we report on the nitroarene hydrogenation capability of a nanostructured nickel catalyst synthesized from a nickel salen complex and a commercially available porous silica support. Our catalyst allows the selective hydrogenation of nitroarenes under mild conditions while tolerating various functional groups and hydrogenation-sensitive examples such as iodine, nitrile or olefinic groups. The use of the nickel salen complex as metal precursor is crucial for the high activity and selectivity observed.

The novel zinc borate Zn2B10O17 was synthesized under high-pressure/high-temperature conditions of 8 GPa and 1573 K in a multianvil apparatus. Single-crystal X-ray diffraction revealed a unique crystal structure that crystallizes in the orthorhombic non-centrosymmetric space group Pmc21 (no. 26) with a=769.15(2), b=711.14(2), c=822.14(2) pm, V=0.450(1) nm3 and two formula units (Z=2) per unit cell. The crystal structure is discussed, SHG measurements, and theoretical calculations at HSEsol level of theory were carried out. Herein, we reported about the novel zinc borate Zn2B10O17. It is synthesizable via high-pressure/high-temperature solid state reactions and features a unique crystal structure in the non-centrosymmetric space group Pmc21 (no. 26), which was confirmed by a SHG-measurement. The structure of Zn2B10O17 consists of an anionic borate framework, that is formed solely by (BO4) units. The zinc atoms are located in channels along the a-axis and are tetrahedrally and octahedrally coordinated by oxygen atoms. The crystal structure was confirmed by MAPLE, CHARDI, and BL/BS calculations. Furthermore, theoretical calculations at HSEsol level were performed to obtain insight into the band structure properties and the DOS of the zinc borate. Zn2B10O17 is a colourless, ionic compound with a wide band gap of 8.4 eV and is therefore categorized as insulator.

A series of three lithium silylamides Li2Me2Si(NC6H4-2-SR)2 (R = Me, Ph, tBu) were prepared from the reaction of the corresponding silylamines Me2Si(NH-C6H4-2-SR)2 with n-butyl lithium. X-ray single crystal structure analyses revealed the formation of dimers [Li4{Me2Si(NC6H4-2-SR)2}2] with Si2N4Li4 hetero-adamantane cores in the solid state. Recrystallisation of [Li4{Me2Si(NC6H4-2-SMe)2}2] and [Li4{Me2Si(NC6H4-2-SPh)2}2] from diethyl ether led to the formation of the adducts [Li4(Et2O)2{Me2Si(NC6H4-2-SMe)2}2] and [Li4(Et2O){Me2Si(N C6H4-2-SPh)2}2]. In the case of the SMe derivative the addition of two diethyl ether molecules led to a rearrangement of the Si2N4Li4 core to give a double decker structure and in contrast the hetero adamantane structure is retained in the diethyl ether adduct of the SPh derivative.

A co-crystal FJU-182 with a closed cage structure with photochromic phenomenon was formed using a tetraphenylene derivatives 4,4′,4′′,4′′′-(anthracene-9,10-diylidenebis(methanediyl-ylidene))tetrabenzoic acid self-assembled with 1,3-di(4-pyridyl)propane in a solvent. It was also found that isomorphic crystals grown from different solvents exhibited different fluorescence. The electron paramagnetic resonance and X-ray photoelectron spectroscopy data showed that the photochromic mechanism of crystal FJU-182 was due to photoinduced electron transfer, while the different color change of crystals grown from different solvents was attributed to the size of solvent molecules. The I−V curves of the crystals FJU-182 before and after illumination were also tested, and it was found that the conductivity of the crystals before the color change would be 3–8 times higher than the conductivity of the crystals after the color development. FJU-182 provides a new case for electrochemical devices with photoelectric response.

Materials with the TiNiSi structure have recently been highlighted as potential thermoelectric materials. Here we report the thermoelectric properties of TiNiX (X=Si and Ge). Both materials behave as defective metals or heavily doped degenerate semiconductors. Room temperature Seebeck coefficients are −45 μV K−1 (Si) and −20 μV K−1 (Ge) with electrical resistivities of 0.5–1 mΩ cm. The lattice thermal conductivities are 8 W m−1 K−1 (Si) and 6 W m−1 K−1 (Ge) at 360 K, which is promising in the absence of alloying. The calculated power factors and figures of merit remain small, with the largest S2/ρ=0.17 mW m−1 K−2 and peak zT=5×10−3 seen in TiNiSi near 300 K. Both compositions show Kondo behaviour at low-temperatures, linked to the emergence of local moment magnetism, and have substantial magnetoresistance effects at 2 K. This work provides property characterisation for two members of this large class of intermetallic materials.

Preparing high-efficiency, durable and low overpotential electrocatalytic materials for oxygen evolution reaction (OER) plays a key role in water electrolysis. At present, electrochemical water separation technology has become the most promising sustainable hydrogen production process. The inherent hysteresis kinetics of oxygen evolution reaction (OER) is the key bottleneck of water electrolysis, which greatly restricts the energy conversion efficiency and practical large-scale application. Herein, a facile method is developed to synthesize a series of trimetallic (Mo/Ni/Fe) metal-organic frameworks (MOFs)-derived carbon nanoparticles (CNPs) with various Fe content, and a Fe-dependent volcano-type plot can be drawn out for MoNiFex-CNPs. The optimized MoNiFe0.4-CNPs demonstrate superior electrocatalytic performance with a low overpotential of only 227 mV@10 mA cm−2 and excellent durability of 100 h. Its excellent OER performance is attributed to the synergistic effect of Fe/Ni bimetallic regulated by Mo. This work improved the catalytic performance of MOFs in the OER and proposed a new strategy for the structural design of MOFs.

This cover picture shows a Lewis adduct between a pyramidal boron Lewis superacid and a bulky pyridine. Due to the high Lewis acidity and pyramidalization at the boron atom, the boron-nitrogen bond is shorter than that in other Lewis adducts. This induces large steric repulsions resulting in the deformation of the collidine Lewis base. This fundamental observation illustrating the importance of the structural reorganization of Lewis bases in a process of association with a bulky Lewis acid is relevant to the field of frustrated Lewis pairs chemistry (DOI: 10.1002/zaac.202300009).

Perovskite solar cells have seen rapid development over the last decade due to their potential to surpass current market-leading solar cell technologies. Power conversion efficiency values of perovskite solar cells have reached more than 25 %, making them comparable to their market-leading silicon-based counterparts with comparatively few years of development. Whilst large-scale trials are ongoing, the long-term stability of perovskite materials remains a significant challenge in their deployment. The first successful perovskite-based solar cells were lead-based (Pb-based). Environmental concerns surrounding Pb-based perovskites are a significant impediment to their application in industry leading to a substantial increase in research into alternatives that are more environmentally sound.

The incorporation of lithium as a filler species in Co1-2xFexNixSb3 skutterudites was accomplished by intercalation at 60 °C, using n-BuLi as a reducing agent. Solid state 7Li NMR and ICP-MS analysis confirm the presence of lithium in the product phases and provide an estimate of the lithium content. The maximum uptake of lithium increases as cobalt is progressively substituted by an equimolar mixture of iron and nickel. Difference Fourier maps, calculated during Rietveld structure refinement using powder neutron diffraction data, locate the lithium cations at the 2a (0,0,0) sites within the cavities of the skutterudite framework. The intercalation of lithium results in reductions in thermal conductivity of up to 47 %, indicative of phonon glass electron crystal (PGEC) type behaviour. Charge transfer from lithium to the framework that accompanies intercalation results in a substantial decrease in electrical resistivity in lithiated phases and a more metal-like temperature dependence. The increased carrier concentration also decreases the Seebeck coefficient, with the consequence that modest increases in the figure of merit occur, despite the reduced thermal conductivity.

With enormous pleasure and honor, we co-edited this Special Issue on the occasion of the 70th birthday of Prof. Doug Stephan, a wonderful colleague, mentor, and friend. His contributions to molecular chemistry are spiked with creativity and of the broadest importance to the field. Doug began his journey in chemistry at McMaster University, where he earned his BSc degree in Chemistry in 1976. Following his undergraduate studies, he moved to the University of Western Ontario to pursue a Ph.D. under the guidance of Prof. Nicholas C. Payne. In 1980, upon completing his Ph.D., he embarked on postdoctoral research at Harvard with Prof. Dick Holm. In 1982, Doug joined the faculty at Windsor, starting his independent research. He remained at Windsor until 2008, when he moved to the University of Toronto, where he currently holds the position of university professor. During the initial stages of his career, Doug's research interests centered around early transition metals and catalysis. He contributed novel insights and an enhanced understanding of ligand design and synthesis for reactivity and catalysis. Throughout the 1980s and 1990s, his work focused on the synthesis and applications of heterobimetallic complexes, specifically in zirconium-phosphorus and titanium-sulfur chemistry. In the mid-1990s, Doug made a groundbreaking discovery of a new class of olefin polymerization catalysts. This development was later commercialized in NOVA Chemical's plant, placing Doug among a select group of chemists whose fundamental breakthroughs have achieved commercial success. In 2006, Doug finally discovered frustrated Lewis pairs (FLPs), comprised of a Lewis acid and a Lewis base that, due to steric hindrance, cannot combine to form a classical adduct. As a result, they are capable of activating small molecules such as H2, CO2, CO, and many others. This finding challenged the long-standing belief that the activation of small molecules and catalysis is solely attributed to transition-metal complexes. His research also demonstrated that FLPs can catalyze various reactions, including hydrogenation, hydrosilylation, dehydrocoupling, C−C bond coupling, CO homologation, and more. The discovery gave rise to an entirely new area of research, which has since become a focal point for numerous research groups worldwide. More importantly, the FLP perspective was quickly and successfully extended to enrich the perception of reactivities at heterogeneous phases, functionalized polymers or frameworks, and simplified several observations from biochemistry to materials science. To this day, Doug remains actively engaged in main-group chemistry, continuously inspiring scientists with his research and support within the scientific community. In addition to being an exceptional scientist, Doug is a highly supportive and inspiring mentor. It is difficult to keep track of how many undergraduates, visiting students, graduate students, and postdoctoral researchers have worked under his mentorship, but it easily surpasses 350 people. Doug has always encouraged his staff to follow their passions and push themselves, this is reflected in the future career endeavors of his alumni. Members of his team have gone on to infiltrate all aspects of society from academics, educators, those working in the chemical industry, to government and policy workers, lawyers and chefs. One of Doug's outstanding leadership qualities is his temperament, where he can approach every situation with empathy, patience, and calmness. He maintains an ‘open-door' policy, making himself highly approachable as his people need additional support, whether in the laboratory or in their personal life. Doug also celebrates the accomplishments of his staff as if he would have himself won that award, scholarship or received that job offer. His mentorship style binds his current team and alumni together. Even those of us with no direct overlap in our time, you will find sharing stories, drinks and celebrating our collective accomplishments at whatever conference it may be. On a personal note, a day that stands out to me (Meera) as a PhD student is when I received my Royal Society Newton Fellowship to undertake postdoctoral research at the University of Oxford. After receiving the confirmation email from the funding body, I was ecstatic and immediately rushed to Doug's office to give him the news. He was behind his desk, and I quickly walked in and blurted it out. He lept from behind his desk and gave me a big hug, he told me he was proud and this was an exceptional opportunity. A few hours later, I ran into him again in the hallway. He told me he had called his wife Diane and she was thrilled for me. In this moment I realized how personally Doug takes the accomplishments of his staff, not only was he proud of me but his first instinct was to share and celebrate this news with those closest to him. Doug is a great scientist and person! This special issue contains a selection of contributions that honor and reflect his broad impact. It illustrates the wide range of chemists inspired by the avenues paved by Doug Stephan. We warmly congratulate Doug on his 70th birthday and look forward to many exciting years to come! Dr. Meera Mehta Prof. Roman Dobrovetsky Prof. Dr. Lutz Greb and on behalf of the editors: Thomas F. Fässler, Christian Limberg, Guodong Qian and David Scheschkewitz. This article is part of a Special Collection dedicated to Professor Doug Stephan on the occasion of his 70th birthday. Please see our homepage for more articles in the collection. Conflict of interest The authors declare no conflict of interest.

The synthesis and characterization of four compounds [M(η5-C5Me5)(N^N)Cl]PF6 [N^N=4,7-dichloro-1,10-phenanthroline with M=Rh, 1, and M=Ir, 2, and N^N=4'-(4-chlorophenyl)-2,2':6',2''-terpyridine in the κ2N,N'-coordination mode with M=Rh, 3, and M=Ir, 4] are described. All compounds were characterized by spectroscopic means and their molecular structures in the crystal were confirmed by single-crystal X-ray diffraction studies. The cytotoxicity of all compounds was evaluated by MTT assay against the three cancer cell lines HeLa (cervical carcinoma), HT-29 (colon adenocarcinoma) and MCF-7 (human breast adenocarcinoma). The complexes 3 and 4 display promising activity with IC50 values of 1 μM. The rhodium(III) complex 1 also shows highly improved cytotoxicity compared to cisplatin against the cancer cell lines HT-29 and MCF-7. In contrast to this, the iridium(III) complex 2 is even less active against the HeLa cell line than cisplatin.

The cover picture presents a structural motif of a distorted Pd2Cl2 square in solid PdCl(NO). This iconic compound was firstly synthesized during outstanding research in the late 1950s in Munich, which led to the development of the Wacker process for the conversion of ethene into acetaldehyde by catalysis with PdCl2. More than sixty years after its synthesis, crystals of PdCl(NO) were prepared for the first time and the structure determined by X-ray diffraction. In the monoclinic structure distorted Pd4Cl4 octagons in chair arrangement are interconnected to corrugated layers, forming a two-dimensional polymer insoluble in common solvents. In this compound each Pd atom is connected to a N-O group, bonded alternatively up and down with a Pd-N-O angle of 129°. The bonding situation in PdCl(NO) was investigated by vibrational, electronic and X-ray absorption (XAS) spectroscopies. The XAS measurement at the KIT synchrotron facility uncovers that the charge located at the Pd atom in PdCl(NO) is comparable to that in PdCl2 or PdO (DOI: 10.1002/zaac.202200337).

Sjoerd Harder (pronounced: sh oo r d, not Sjörd, as most of the German colleagues tend to say and write …!) was born on March 17, 1963, in Grootegast, The Netherlands. Growing up in a village in West Friesland, close to Groningen and the North Sea, probably explains why Sjoerd developed a very strong connection to nature and a passion for sailing, hiking, travelling, seafood but especially good food in general, beer (lekker biertje …), wine and whiskey or distilled drinks in general. In 1981, Sjoerd moved to the centre of the Netherlands to study Chemistry and Physics at the University of Utrecht. He completed his Master's degree in Chemistry with a thesis in organometallic chemistry (Dr. Jaap Boersma) and a thesis in crystallography (Prof. Dr. Jan Kroon and Dr. Jan Kanters) in 1986 with cum laude, which refers to the top 5 % of the candidates in the Dutch academic system. A key moment in his life, which certainly influenced his later highly successful career, was when joining the group of Prof. Dr. Lambert Brandsma, a wizard of organic chemistry – especially using alkali metal organics. Sjoerd defended his thesis entitled “A study on the structure and reactivity of aryllithium compounds with an α- or β-heteroatom” again with cum laude and in 1991 he moved to the University of Erlangen-Nürnberg in Germany as a postdoctoral fellow with a scholarship from the Alexander von Humboldt foundation. In the group of Prof. Dr. Paul von Ragué Schleyer, Sjoerd was introduced to ab initio calculations. In 1992, with a NATO-Fellowship of the Netherlands Organization for Scientific Research (NWO) in his pocket, he subsequently moved to the University of California at Berkeley (USA) for a second postdoc with Prof. Dr. Andrew Streitwieser, working on heterobimetallic superbases. In 1993, Sjoerd decided to move back to Germany to join the group of Prof. Dr. Hans-Herbert Brintzinger at the University of Konstanz. This postdoctoral period was supported by a fellowship from the Alexander von Humboldt foundation and two fellowships from the European Union (Human Capital & Mobility and Marie Curie). While still in Konstanz, Sjoerd began his habilitation in inorganic and organometallic chemistry, which he successfully completed in 1998. Sjoerd stayed in Konstanz as a lecturer, where he also met his wonderful wife from Ireland, and enjoyed several intermezzi as a guest lecturer at the University of Cape Town (South Africa) before he became C3 Professor of Inorganic and Organometallic Chemistry at the University of Duisburg-Essen in 2004. After five years in Essen, Sjoerd wanted to move on. He declined a W3 position for Inorganic Chemistry at the University of Konstanz and, instead, accepted in 2010 the chair of Molecular Inorganic Chemistry at the University of Groningen, The Netherlands. However, after only two years, Sjoerd decided to move again back to Germany and accepted a chair position in Inorganic Chemistry at the University of Erlangen-Nürnberg, where he has been since 2012. Sjoerd has a passion for main group chemistry. He is particularly well known for his inspiring work on Group 1 and Group 2 chemistry. His seminal papers on “The Simplest Metallocene Sandwich: The Lithocene Anion“ (Angew. Chem. Int. Ed. Engl. 1994, 22, 1744) and on “Rational Design of a Well-Defined Soluble Calcium Hydride Complex” (Angew. Chem. Int. Ed. Engl. 2006, 45, 3474) and, related to that, “Early Main-Group Metal Catalysts for the Hydrogenation of Alkenes with H2” (Angew. Chem. Int. Ed. 2008, 47, 9434) were truly exceptional and ground breaking. In recent years, his work has been extended to the activation of aromatic systems and strong C−H bonds by main group metal cocktails, the synthesis and reactivity of low-valent main group metal complexes and sustainable catalytic processes with main group metals. Sjoerd's exceptional scientific productivity is reflected in numerous quality publications, books and conference contributions. For his pioneering work in the field of s-block metal chemistry, in particular alkaline earth metal catalysis, Sjoerd received in 2017 the Schlenk Lecture Award of the University of Tübingen and BASF. This was followed by the Main Group Chemistry Award of the Royal Society of Chemistry in 2020. Sjoerd is also known for being an exceptional teacher (especially when it comes to doing experiments …), an enthusiastic lecturer, a very good advisor and a supportive mentor. Apart from being a seasoned researcher, Sjoerd is a warm, humorous and reliable colleague. It was a joy to work with him and we have fond memories of the friday night “Feierabend” beers and the many personal encounters. Thank you for your long-lasting friendship and congratulations on your 60th birthday. We wish you all the best and look forward to many more years of fascinating chemistry emerging from your laboratories. Stephan Schulz Christian Müller Conflict of interest The authors declare no conflict of interest.

The structure of the new compound GaGe2Te has been determined using nanofocused synchrotron radiation. The trigonal structure (space group P m1, a=4.0443(3) Å, c=14.923(2) Å, V=211.38(4) Å3; Z=2) consists of Ge bilayers sandwiched by Ga−Te layers. Ge and Ga are tetrahedrally coordinated. The layer packages are separated by a van der Waals gap with a Te−Te distance of 4.1502(7) Å. The structure resembles that of GaGeTe but features an additional Ge atom layer. Despite small scattering contrast of Ga and Ge, precise high-resolution data enable unequivocal atom assignment as confirmed by R values of different models. DFT calculations suggest only a small extent of charge transfer, which is confirmed by both Bader and Mulliken charges. Thus, bonding within the layer packages is predominantly covalent, especially between Ga and Ge. Formal oxidation states according to GaIIIGe(0)Ge−ITe−II, i. e. assuming rather ionic Ge−Ga bonds, convey a much less realistic situation than GaIIGe2(0)Te−II, which is in line with GaGeTe.

Half-sandwich iridium complexes of the type [(η5-C5Me5){(NHC)E}IrCl] (E=P, As) were prepared by the reactions of N-heterocyclic carbene (NHC) adducts of trimethylsilylphosphinidene and trimethylsilylarsinidene, (IDipp)ESiMe3 and (IMes)ESiMe3, with [(η5-C5Me5)IrCl2]2 (IDipp=bis(2,6-diisopropylphenyl)imidazolin-2-ylidene; IMes=1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene). The molecular structure of [(η5-C5Me5){(IDipp)As}IrCl] was established by X-ray diffraction analysis, affording the first structurally authenticated NHC-arsinidenide complex with a short Ir−As bond length that reveals a significant degree of metal-arsenic π-interaction as also confirmed by theoretical calculations.

Herein, we report two hybrid zero-dimensional (0D) lead-free metal oxide halides of [PPip]Sb2Cl6O (1) ([PPip]=1-(2-Pyridyl)piperazine) and [PmPip]Sb2Cl6O (2) ([PmPip]=1-(2-Pyrimidyl)piperazine). Compounds 1 and 2 are able to exhibit narrow blue light emissions excited by UV light with photo-luminescence quantum yields (PLQYs) of 25.49 % and 24.71 %, respectively. Through systematical characterizations, these blue light emissions can be attributed to the radiative transition in conjugated organic cations. Benefiting from the highly efficient intrinsic blue emissions, compound 2 can be used as blue fluorophor to fabricate liquid crystal display. This work provides a new to assembly blue emitter through by virtue of the optical active organic cations in hybrid materials.

Polychalcogenides REX2-δ (X=S, Se, Te; 0≤δ≤0.2) of trivalent rare earth metals RE have been investigated in recent years to shed light on the structural diversity as a function of compositional, metric, thermodynamic, and electronic situation. Whereas the former aspects have comparable influence on the structures of all polychalcogenides REX2-δ, the bonding situation was assumed different for tellurides due to tellurium's higher tendency to delocalize electrons. The crystal structures generally contain puckered [REX] double slabs and planar [X] layers, the latter hosting different distortions from a square-like arrangement. The distortion patterns of sulfides and selenides can be understood by a Zintl-type approach; they are dominated by localization of valence electrons in mono- (X2−) or dinuclear (X22−) anions only. This review discusses crystal structures of some rare-earth metal polytellurides RETe2-δ (0≤δ≤0.2) and bonding features in the chalcogenide layers and relates them to their sulfide and selenide counterparts.

Black needle-shaped crystals of the bismuth-rich mixed halogenide Bi21Rh4Cl6I7 were obtained by slow cooling of a melt of Bi, RhI3 and BiCl3. Single-crystal X-ray diffraction revealed an orthorhombic structure that consists of infinite intermetallic rods [[EQUATION]]Bi9Rh2]3+ and discrete anionic groups [BiII2Cl2I5]3– and [BiIIICl4I2]3–. The rods consist of Rh-centered [RhBi8] polyhedra that alternately share triangular and rectangular faces. Using traditional electron counting rules, the rod can be interpreted as a covalent polymer with Rh2 dumbbells bonded to molecular Bi2 and Bi5 units. However, a quantum-chemical bonding analysis shows that the bonds involving Rh atoms are largely diffuse, while two-center bonds dominate in the bismuth units. The below 240 K observed semiconducting behavior of Bi21Rh4Cl6I7 is consistent with a complete localization of the valence electrons. Above 240 K, the resistance along the needle axis is largely independent of temperature.

Exploring synthesis methods fosters new ways to design materials in faster and cheaper ways. In this fundamental study, we present mechanochemical loading of photoactive dye molecules into porous metal-organic frameworks (=MOFs) as an alternative and promising strategy to form hybrid switch@MOF systems. Six different spiropyrans were inserted into the two MOFs MOF-5 and MIL-68(In) in varying compositions. By this, the concentration-dependent enclosure characteristics were determined. This fast and simple synthesis strategy has never been reported so far, and thus provides completely new possibilities for the formation of two- or even multi-component systems.