Assembly, Thermodynamics, and Structure of a Two-Wheeled Composite of a Dumbbell-Shaped Molecule and Cylindrical Molecules with Different Edges.

A carbonaceous dumbbell was able to spontaneously glue two tubular receptors to form a unique two-wheeled composite through van der Waals interactions, thus forcing the wheel components into contact with each other at the edges. In the present study, two tubular receptors with enantiomeric carbon networks were assembled on the dumbbell joint, and the handedness of the receptors was discriminated, thus leading to the self-sorting of homomeric receptors from a mixture of enantiomeric tubes. The crystal structures of the composites revealed the structural origins of the molecular recognition driven by van der Waals forces as well as the presence of a columnar array of C molecules in a 1:1 composite.

Self-Sorting of Two Hydrocarbon Receptors with One Carbonaceous Ligand.

Non-directional van der Waals forces in biological and synthetic supramolecular systems play important roles in molecular assembly, particularly in determining the distances of the interacting species. The van der Waals forces are normally used in combination with other directional forces and are considered to play a secondary role in achieving specificity and fidelity in molecular recognition. Using an ideal supramolecular system consisting solely of hydrogen and carbon atoms, we found that the van der Waals interactions enable the high-fidelity sorting of two homomeric receptors during ligand-induced assembly.

An isoelectronic NO dioxygenase reaction using a nonheme iron(III)-peroxo complex and nitrosonium ion.

Reaction of a nonheme iron(III)-peroxo complex, [Fe(III)(14-TMC)(O2)](+), with NO(+), a transformation which is essentially isoelectronic with that for nitric oxide dioxygenases [Fe(III)(O2˙(-)) + NO], affords an iron(IV)-oxo complex, [Fe(IV)(14-TMC)(O)](2+), and nitrogen dioxide (NO2), followed by conversion to an iron(III)-nitrato complex, [Fe(III)(14-TMC)(NO3)(F)](+).

Reactions of a chromium(III)-superoxo complex and nitric oxide that lead to the formation of chromium(IV)-oxo and chromium(III)-nitrito complexes.

The reaction of an end-on Cr(III)-superoxo complex bearing a 14-membered tetraazamacrocyclic TMC ligand, [Cr(III)(14-TMC)(O2)(Cl)](+), with nitric oxide (NO) resulted in the generation of a stable Cr(IV)-oxo species, [Cr(IV)(14-TMC)(O)(Cl)](+), via the formation of a Cr(III)-peroxynitrite intermediate and homolytic O-O bond cleavage of the peroxynitrite ligand. Evidence for the latter comes from electron paramagnetic resonance spectroscopy, computational chemistry and the observation of phenol nitration chemistry. The Cr(IV)-oxo complex does not react with nitrogen dioxide (NO2), but reacts with NO to afford a Cr(III)-nitrito complex, [Cr(III)(14-TMC)(NO2)(Cl)](+).

Chromium(IV)-peroxo complex formation and its nitric oxide dioxygenase reactivity.

The O(2) and NO reactivity of a Cr(II) complex bearing a 12-membered tetraazamacrocyclic N-tetramethylated cyclam (TMC) ligand, [Cr(II)(12-TMC)(Cl)](+) (1), and the NO reactivity of its peroxo derivative, [Cr(IV)(12-TMC)(O(2))(Cl)](+) (2), are described. By contrast to the previously reported Cr(III)-superoxo complex, [Cr(III)(14-TMC)(O(2))(Cl)](+), the Cr(IV)-peroxo complex 2 is formed in the reaction of 1 and O(2). Full spectroscopic and X-ray analysis revealed that 2 possesses side-on η(2)-peroxo ligation.

Remarkable enhancement of catalytic activity of a 2 : 1 complex between a non-planar Mo(v)-porphyrin and a ruthenium-substituted Keggin-type heteropolyoxometalate in catalytic oxidation of benzyl alcohols.

A 2 : 1 complex composed between a non-planar Mo(v)-porphyrin complex ([Mo(DPP)(O)](+), DPP(2-) = dodecaphenylporphyrin) and a ruthenium-substituted Keggin-type heteropolyoxometalate (Ru-POM), [SiW(11)O(39)Ru(III)(DMSO)](5-), acts as an efficient catalyst for oxidation of benzyl alcohols with iodosobenzene as an oxidant in CDCl(3) at room temperature. The catalytic oxidation afforded the corresponding benzaldehydes, whereas neither the ammonium salt of Ru-POM nor [Mo(DPP)(O)](+) alone exhibited catalytic reactivity under the same experimental conditions. This enhancement can be attributed to a large anodic shift of the redox potential of the ruthenium centre due to the complexation of the Ru-POM with two cationic {Mo(DPP)(O)}(+) units.

Enclosure of a Keggin-type heteropolyoxometalate into a tubular π-space via hydrogen bonds with a nonplanar Mo(V)-porphyrin complex forming a supramolecular assembly.

A 2:1 supramolecular assembly composed of a non-planar Mo(V)-porphyrin, [Mo(DPP)(O)(H(2)O)](+) (1) (DPP(2+); dodecaphenylporphyrin), and a Keggin-type heteropolyoxometalate (POM), α-[(n-butyl)(4)N](2)[SW(12)O(40)] (2), was formed via hydrogen bonds. The crystal structure was determined by X-ray crystallography to clarify that the POM was enclosed into a π-space of a supramolecular porphyrin nanotube by virtue of a hydrogen-bond network. In contrast to the formation of the 2:1 assembly ([{Mo(DPP)(O)(H(2)O)}(2)(SW(12)O(40))] (3)) between 1 and [SW(12)O(40)](2-) in the crystal, it was revealed that those two components form a 1:1 assembly in solution, in light of the results of MALDI-TOF-MS measurements in PhCN.

Formation of a hybrid compound composed of a saddle-distorted Tin(IV)-porphyrin and a Keggin-type heteropolyoxometalate to undergo intramolecular photoinduced electron transfer.

Nonplanar Sn(IV)-porphyrin complexes, [Sn(TMPP(Ph)(8))-Cl(2)] (1) and [Sn(TMPP(Ph)(8))(OMe)(2)] (2) (TMPP(Ph)(8): 5,10,15,20-tetrakis(4-methoxyphenyl)-2,3,7,8,12,13,17,18-octaphenylporphyrinato), were prepared and characterized by spectroscopic and electrochemical methods together with X-ray crystallography. Variable-temperature (1)H NMR study revealed that the coordination of the methoxo ligand of 2 is weak enough in solution to enhance the axial ligand exchange with a Keggin-type phosphotungstate (α-[PW(12)O(40)](3-)) due to the steric stress between the axial methoxo ligand and the peripheral phenyl groups of the porphyrin ligand. The formation of a novel 1:1 donor-acceptor complex, [Sn(TMPP(Ph)(8))(OMe)(α-[PW(12)O(40)])](2-) (4) was confirmed by (1)H NMR and UV-vis spectral titrations, and also by MALDI-TOF-MS measurements.

Crystal structures and solution properties of discrete complexes composed of saddle-distorted molybdenum(v)-dodecaphenylporphyrins and keggin-type heteropolyoxometalates linked by direct coordination.

Reactions of a saddle-distorted Mo(V)-porphyrin complex, [Mo(DPP)(O)(H(2)O)]ClO(4) (1·ClO(4); DPP(2-) = dodecaphenylporphyrin dianion), with tetra-n-butylammonium (TBA) salts of Keggin-type heteropolyoxomatalates (POMs), α-[XW(12)O(40)](n-) (X = P, n = 3, 2; X = Si, n = 4, 3; X = B, n = 5; 4), in ethyl acetate/acetonitrile gave 2:1 complexes formulated as [{Mo(DPP)(O)}(2)(HPW(12)O(40))] (5), [{Mo(DPP)(O)}(2)(H(2)SiW(12)O(40))] (6), and [(n-butyl)(4)N](2)[{Mo(DPP)(O)}(2)(HBW(12)O(40))] (7) under mild reaction conditions. The crystal structures of the complexes were determined by X-ray crystallography. In these three complexes, named Porphyrin Hamburgers, the POM binds to two Mo(V) centers of porphyrin units directly via coordination of two terminal oxo groups.

A discrete conglomerate of a distorted Mo(v)-porphyrin with a directly coordinated Keggin-type polyoxometalate.

The reaction of a saddle-distorted Mo(v)-dodecaphenylporphyrin complex and a Keggin-type polyoxometalate gives a discrete and nanosized molecule, [{Mo(DPP)(O)}(2)(H(2)SiW(12)O(40))], which involves direct coordination between the Mo(v) centers and terminal oxo groups of the polyoxometalate and exhibits excellent stability in solution to show reversible multi-redox processes.