A convenient access to a triad of triazoles with ferrocenyl and cobaltoceniumyl substituents is reported. N‐Alkylation, deprotonation and metalation with CuI/AgI/AuI synthons affords the heteroleptic triazolylidene complexes. Due to the combination of neutral, electron‐donating ferrocenyl substituents and cationic, strongly electron‐withdrawing cobaltocenium substituents, the mesoionic carbene (MIC) ligands of these complexes are electronically interesting “push–pull”, “pull–push” and “pull–pull” metalloligands with further switchable redox states based on their fully reversible FeII/FeIII, (ferrocene/ferrocenium) and CoIII/CoII, (cobaltocenium/cobaltocene) redox couples. These are the first examples of metal complexes of (di)cationic NHC ligands based on cobaltoceniumyl substituents. DFT calculated Tolman electronic parameter (TEP) of the new MIC ligands, show these metalloligands to be extremely electron‐poor NHCs with properties unmatched in other carbene chemistry. Utilization of these multimetallic electronically tunable compounds in catalytic oxazoline synthesis and in antitumor studies are presented. Remarkably, 1 mol % of the AuI complex with the dicationic MIC ligand displays full catalytic conversion, without the need for any other additives, in less than 2 hours at ambient temperatures. These results thus firmly establish these new classes of cobaltoceniumyl based (di)cationic MIC ligands as prominent players in several branches of chemistry.

We present here anionic borate based bi-mesoionic carbene compounds (with additional cyclohexyl or phenyl substituents on borate) that undergo C-N isomerization reactions. The isomerized compounds are excellent ligands for Co II centers. Strong agostic interactions with the "C-H"-groups of the cyclohexyl substituents result in an unusual low spin square planar Co II complex, which is unreactive towards external substrates. Such agostic interactions are absent in the complex with phenyl substituents on the borate backbone. That complex displays a high spin tetrahedral Co II center, which is reactive towards external substrates including dioxygen. A combined synthetic, crystallographic, spectroscopic and theoretical approach is used to investigate the compounds. We conclusively show here that the structure and properties of these Co II complexes can be strongly influenced through interactions in the secondary coordination sphere. Additionally, we unravel a unique ligand rearrangement for these classes of anionic mesoionic carbene based ligands.

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Hybridizing graphene and molecules possess a high potential for developingm aterials for new applications. However,n ew methods to characterize such hybrids must be developed. Herein,t he wet-chemical non-covalent functionalizationo fg raphene with cationic p-systems is presented and the interactionbetween graphene and the molecules is characterizedi nd etail. As eries of tricationic benzimidazolium salts with variouss tericd emand and counterions was synthesized, characterizeda nd used for the fabrication of graphene hybrids. Subsequently,t he doping effects were studied. The molecules are adsorbed onto graphene and studied by Ramans pectroscopy,X PS as well as ToF-SIMS. The charged p-systems show ap -doping effect on the underlyingg raphene. Consequently,t he tricationic molecules are reduced through ap artial electron transfer processf rom graphene, ap rocess which is accompanied by the loss of counterions. DFT calculations support this hypothesis and the strong p-doping could be confirmed in fabricatedm onolayer graphene/hybrid FET devices.T he resultsa re the basis to develops ensora pplications, which are based on analyte/ molecule interactions and effects on doping.

Diradicals have been of tremendous interest for over a century ever since the first reports of p‐ and m‐phenylene‐bridged diphenylmethylradicals in 1904 by Thiele and 1915 by Schlenk. Reported here are the first examples of cyclic(alkyl)(amino)carbene (CAAC) analogues of Thiele's hydrocarbon, a Kekulé diradical, and Schlenk's hydrocarbon, a non‐Kekulé diradical, without using CAAC as a precursor. The CAAC analogue of Thiele's hydrocarbon has a singlet ground state, whereas the CAAC analogue of Schlenk's hydrocarbon contains two unpaired electrons. The latter forms a dimer, by an intermolecular double head‐to‐tail dimerization. This straightforward synthetic methodology is modular and can be extended for the generation of redox‐active organic compounds.

Vibrational energy relaxation is of critical importance for the lightcontrolled reactivity of transition-metal complexes. In time-resolved optical spectroscopies, it gives rise to pronounced spectral redistributions with complex band shifts and thus to nonexponential kinetics, all of which are very difficult to quantify. Here we study the vibrational relaxation dynamics of a pentacoordinated azido−cobalt(II) complex in liquid solution following its ultrafast charge-transfer excitation in the near-ultraviolet (UV). The complex is photochemically remarkably stable and returns within the experimental time resolution back to its quartet electronic ground state via internal conversion. The nonadiabatic transition effectively instantaneously converts the entire photon energy into kinetic energy of the vibrational degrees of freedom. The ensuing relaxation dynamics of the vibrationally highly excited complex are monitored as a function of time using femtosecond mid-infrared (MIR) spectroscopy in the antisymmetric stretching region of the azido ligand and occur on a time scale of a few tens of picoseconds. The dynamic evolution of the MIR spectrum due to vibrational cooling of the complex can be understood quantitatively within the framework of an anharmonic coupling model, which relies on an ab initio intramolecular cubic/quartic force field from density functional theory combined with second-order vibrational perturbation theory. The simulations suggest that the primary internal conversion preferentially dumps the excess energy into the low-frequency bending modes of the azido ligand, whereas its high-frequency stretching modes are barely affected by the initial nonadiabatic transition. Surprisingly, the two bending vibrations appear to relax independently of one another, each with its own characteristic cooling time.

This work presents a stepwise reversible two‐electron transfer induced hydrogen shift leading to the conversion of a bis‐pyrrolinium cation to an E‐diaminoalkene and vice versa. Remarkably, the forward and the reverse reaction, which are both reversible, follow two completely different reaction pathways. Establishing such unprecedented property in this type of processes was possible by developing a novel synthetic route towards the starting dication. All intermediates involved in both the forward and the backward reactions were comprehensively characterized by a combination of spectroscopic, crystallographic, electrochemical, spectroelectrochemical, and theoretical methods. The presented synthetic route opens up new possibilities for the generation of multi‐pyrrolinium cation scaffold‐based organic redox systems, which constitute decidedly sought‐after molecules in contemporary chemistry.

A new, palladium-free Sonogashira coupling reaction protocol using a catalytic system that comprises a simple, cheap, widely available copper salt and a chelating 1,2,3-triazolylidene ligand precursor is reported. This protocol provides the desired coupling products in moderate to very good yields.