Important electromeric states in manganese-oxo porphyrins MnO(P)(+) and MnO(PF4)(+) (porphyrinato or meso-tetrafluoroporphyrinato) have been investigated with correlated ab initio methods (CASPT2, RASPT2), focusing on their possible role in multistate reactivity patterns in oxygen transfer (OAT) reactions. Due to the lack of oxyl character, the Mn(V) singlet ground state is kinetically inert. OAT reactions should therefore rather proceed through thermally accessible triplet and quintet states that have a more pronounced oxyl character. Two states have been identified as possible candidates: a Mn(V) triplet state and a Mn(IV)O(L(•)a2u)(+) quintet state. The latter state is high-lying in MnO(P)(+) but is stabilized by the substitutions of H by F at the meso carbons (where the a2u orbital has a significant amplitude). Oxyl character and Mn-O bond weakening in these two states stems from the fact that the Mn-O π* orbitals become singly (triplet) or doubly occupied (quintet). Moreover, an important role for the reactivity of the triplet state is also likely to be played by the π bond that has an empty π* orbital, because of the manifest diradical character of this π bond, revealed by the CASSCF wave function. Interestingly, the diradical character of this bond increases when the Mn-O bond is stretched, while the singly occupied π* orbital looses its oxygen radical contribution. The RASPT2 results were also used as a benchmark for the description of excited state energetics and Mn-O oxyl character with a wide range of pure and hybrid density functionals. With the latter functionals both the Mn(V) → Mn(IV) promotion energy and the diradical character of the π bond (with empty π*) are found to be extremely dependent on the contribution of exact exchange. For this reason, pure functionals are to be preferred.

Reaction of the Co I complex [(TIMMN mes )Co I ](PF 6 ) (1) (TIMMN mes = tris-[2-(3-mesityl-imidazolin-2-ylidene)-methyl]amine) with mesityl azide yields the Co III imide [(TIMMN mes )Co III (NMes)]-(PF 6 ) (2). Oxidation of 2 with [FeCp 2 ](PF 6 ) provides access to a rare Co III imidyl [(TIMMN mes )Co(NMes)]-(PF 6 ) 2 ( 3). Single-crystal X-ray diffractometry and EPR spectroscopy confirm the molecular structure of 3 and its S = 1 = 2 ground state. ENDOR, X-ray absorption spectroscopy and computational analyses indicate a ligand-based oxidation; thus, an imidyl-radical electronic structure for 3. Migratory insertion of one ancillary NHC to the imido ligand in 2 gives the Co I Nheterocyclic imine (4) within 12 h. Conversely, it takes merely 0.5 h for 3 to transform to the Co II congener (5). The migratory insertion in 2 occurs via a nucleophilic attack of the imido ligand at the NHC to give 4, whereas in 3, a nucleophilic attack of the NHC at the electrophilic imidyl ligand yields 5. The reactivity shunt upon oxidation of 2 to 3 confirms an umpolung of the imido ligand.

Here we report chemically induced folding of thin graphene flakes. The folding occurs spontaneously when an intercalating species interrupts the adhesion between graphene and a supporting substrate. The morphology of induced folds suggests that the conjugated pi network is capable of extremely sharp curvature. Adjacent folds are often parallel, suggesting preferential deformation along certain crystallographic planes.

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As key intermediates in metal-catalyzed nitrogen-transfer chemistry, terminal imido complexes of iron have attracted significant attention for a long time. In search of versatile model compounds, the recently developed second-generation N-anchored tris-NHC chelating ligand tris-[2-(3-mesityl-imidazole-2-ylidene)-methyl]amine (TIMMNMes) was utilized to synthesize and compare two series of mid- to high-valent iron alkyl imido complexes, including a reactive Fe(V) adamantyl imido intermediate en route to an isolable Fe(V) nitrido complex. The chemistry toward the iron adamantyl imides was achieved by reacting the Fe(I) precursor [(TIMMNMes)FeI(N2)]+ (1) with 1-adamantyl azide to yield the corresponding trivalent iron imide. Stepwise chemical reduction and oxidation lead to the isostructural series of low-spin [(TIMMNMes)Fe(NAd)]0,1+,2+,3+ (2 Ad –5 Ad ) in oxidation states II to V. The Fe(V) imide [(TIMMNMes)Fe(NAd)]3+ (5 Ad ) is unstable under ambient conditions and converts to the air-stable nitride [(TIMMNMes)FeV(N)]2+ (6) via N–C bond cleavage. The stability of the pentavalent imide can be increased by derivatizing the nitride [(TIMMNMes)FeIV(N)]+ (7) with an ethyl group using the triethyloxonium salt Et3OPF6. This gives access to the analogous series of ethyl imides [(TIMMNMes)Fe(NEt)]0,1+,2+,3+ (2 Et –5 Et ), including the stable Fe(V) ethyl imide. Iron imido complexes exist in a manifold of different electronic structures, ultimately controlling their diverse reactivities. Accordingly, these complexes were characterized by single-crystal X-ray diffraction analyses, SQUID magnetization, and electrochemical methods, as well as 57Fe Mössbauer, IR vibrational, UV/vis electronic absorption, multinuclear NMR, X-band EPR, and X-ray absorption spectroscopy. Our studies are complemented with quantum chemical calculations, thus providing further insight into the electronic structures of all complexes.

The combination of organic and inorganic molecular building blocks gives rise to hybrid supramolecular materials showing properties from both chemical domains. This work presents the synthesis of metallopolymers made from poly(4-vinylpyridine) (P4VP) and pentacyanoferrate(II) at various polymer repeating unit/[Fe(CN)(5)](3-) ratios (py/Fe) and focuses on the influence of each block on the properties of the other. The solvatochromic shift of the [Fe(CN)(5)](3-) moiety was investigated as a function of the py/Fe ratio and the water molar fraction (X(H(2)O)) of the ethanol/water medium. Asymmetric solvation favoring ethanol was enhanced as the py/Fe ratio increased. The results lead to a modification of the well-established thermodynamical model for asymmetrical solvation and suggest the formation of water-rich domains within the polymer coils with a large number of [Fe(CN)(5)](3-) units. From the macromolecular perspective, the increase of [Fe(CN)(5)](3-) units resulted in higher values of intrinsic viscosity, which is rationalized by the increase of the polymer coil charge density and therefore the increase in hydrodynamic volume due to repulsive electrical forces. Evaluating the intrinsic viscosity of a sample with py/Fe = 25 in solvent mixtures with different water molar fractions, it was found that the hydrodynamic volume is maximized at intermediate X(H(2)O) values, where both the ethanol-soluble uncomplexed polymer block and the water-soluble [Fe(CN)(5)](3-)-pendant units can be suitably solvated, preventing coil shrinkage.

The synthesis, characterization, and reactivity of a series of cobalt terminal imido complexes supported by an Nanchored tripodal tris(carbene) chelate is described, including a Cosupported singlet nitrene. Reaction of the Co I precursor [(TIMMN mes )Co I ](PF 6 ) (TIMMN mes = tris- [2-(3-mesityl-imidazolin-2-ylidene)-methyl]amine) with p-methoxyphenyl azide yields a Co III imide [(TIMMN mes )Co III (NAnisole)](PF 6 ) (1). Treatment of 1 with 1 equiv of [FeCp 2 ](PF 6 ) at −35 °C affords a formal Co IV imido complex [(TIMMN mes )Co(NAnisole)](PF 6 ) 2 (2), which features a bent Co−N(imido)−C(Anisole) linkage. Subsequent one-electron oxidation of 2 with 1 equiv of AgPF 6 provides access to the tricationic cobalt imido complex [(TIMMN mes )Co-(NAnisole)](PF 6 ) 3 (3). All complexes were fully characterized, including single-crystal X-ray diffraction (SC-XRD) analyses, infrared (IR) vibrational, ultraviolet/visible (UV/vis) electronic absorption, multinuclear NMR, X-band electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR), and high-energy-resolution fluorescence-detected X-ray absorption spectroscopy (HERFD XAS). Quantum chemical calculations provide additional insight into the electronic structures of all compounds. The dicationic Co IV imido complex 2 exhibits a doublet ground state with considerable imidyl character as a result of covalent Co−NAnisole bonding. At room temperature, 2 readily converts to a Co II amine complex involving intramolecular C−H bond amination. Electronically, tricationic complex 3 can be understood as a singlet nitrene bound to Co III with significant Co IV imidyl radical character. Verifying the pronounced electrophilicity, nucleophiles such as H 2 O and t BuNH 2 add to 3�analogous to the parent free nitrene�in the para position of the aromatic substituent, thus, clearly corroborating singlet nitrene-type reactivity.