Synthesis, Characterization, and Efficient Catalytic Activities of a Nickel(II) Porphyrin: Remarkable Solvent and Substrate Effects on Participation of Multiple Active Oxidants.

A new nickel(II) porphyrin complex, [NiII (porp)] (1), has been synthesized and characterized by 1 H NMR, 13 C NMR and mass spectrometry analysis. This NiII porphyrin complex 1 quantitatively catalyzed the epoxidation reaction of a wide range of olefins with meta-chloroperoxybenzoic acid (m-CPBA) under mild conditions. Reactivity and Hammett studies, H218 O-exchange experiments, and the use of PPAA (peroxyphenylacetic acid) as a mechanistic probe suggested that participation of multiple active oxidants NiII -OOC(O)R 2, NiIV -Oxo 3, and NiIII -Oxo 4 within olefin epoxidation reactions by the nickel porphyrin complex is markedly affected by solvent polarity, concentration, and type of substrate. In aprotic solvent systems, such as toluene, CH2 Cl2 , and CH3 CN, multiple oxidants, NiII -(O)R 2, NiIV -Oxo 3, and NiIII -Oxo 4, operate simultaneously as the key active intermediates responsible for epoxidation reactions of easy-to-oxidize substrate cyclohexene, whereas NiIV -Oxo 3 and NiIII -Oxo 4 species become the common reactive oxidant for the difficult-to-oxidize substrate 1-octene. In a protic solvent system, a mixture of CH3 CN and H2 O (95:5), the NiII -OOC(O)R 2 undergoes heterolytic or homolytic O-O bond cleavage to afford NiIV -Oxo 3 and NiIII -Oxo 4 species by general acid catalysis prior to direct interaction between 2 and olefin, regardless of the type of substrate. In this case, only NiIV -Oxo 3 and NiIII -Oxo 4 species were the common reactive oxidant responsible for olefin epoxidation reactions.

Transtendinous wiring of mallet finger fractures presenting late.

PURPOSE: To determine if transtendinous wiring was an effective late treatment for bony mallet injuries. METHODS: Between 2005 and 2011, 19 consecutive patients (13 men, 6 women) with a mean age of 29 years (range, 13-52 y) were treated late for mallet finger fractures. The mean interval from injury to initial operation was 57 days (range, 28-141 d). RESULTS: Fifteen of 18 mallet fractures demonstrated evidence of radiographic healing after an average of 6 weeks (range, 5-10 wk). One patient developed ankylosis, and 3 patients failed to achieve bone union at the final follow-up. The mean motion of the distal interphalangeal joint was 73° (range, 35°-95°), and the mean extension lag was 7° (range, 0°-25°). CONCLUSIONS: Transtendinous wiring was an effective late treatment for mallet fractures, demonstrating satisfactory fixation, allowing early mobilization, and showing good functional results while avoiding salvage operations. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.

Remarkable solvent, porphyrin ligand, and substrate effects on participation of multiple active oxidants in manganese(III) porphyrin catalyzed oxidation reactions.

The participation of multiple active oxidants generated from the reactions of two manganese(III) porphyrin complexes containing electron-withdrawing and -donating substituents with peroxyphenylacetic acid (PPAA) as a mechanistic probe was studied by carrying out catalytic oxidations of cyclohexene, 1-octene, and ethylbenzene in various solvent systems, namely, toluene, CH(2) Cl(2) , CH(3) CN, and H(2) O/CH(3) CN (1:4). With an increase in the concentration of the easy-to-oxidize substrate cyclohexene in the presence of [(TMP)MnCl] (1a) with electron-donating substituents, the ratio of heterolysis to homolysis increased gradually in all solvent systems, suggesting that [(TMP)Mn-OOC(O)R] species 2a is the major active species. When the substrate was changed from the easy-to-oxidize one (cyclohexene) to difficult-to-oxidize ones (1-octene and ethylbenzene), the ratio of heterolysis to homolysis increased a little or did not change. [(F(20) TPP)Mn-OOC(O)R] species 2b generated from the reaction of [(F(20) TPP)MnCl] (1b) with electron-withdrawing substituents and PPAA also gradually becomes involved in olefin epoxidation (although to a much lesser degree than with [(TMP)Mn-OOR] 2a) depending on the concentration of the easy-to-oxidize substrate cyclohexene in all aprotic solvent systems except for CH(3) CN, whereas Mn(V)=O species is the major active oxidant in the protic solvent system. With difficult-to-oxidize substrates, the ratio of heterolysis to homolysis did not vary except for 1-octene in toluene, indicating that a Mn(V)=O intermediate generated from the heterolytic cleavage of 2b becomes a major reactive species. We also studied the competitive epoxidations of cis-2-octene and trans-2-octene with two manganese(III) porphyrin complexes by meta-chloroperbenzoic acid (MCPBA) in various solvents under catalytic reaction conditions. The ratios of cis- to trans-2-octene oxide formed in the reactions of MCPBA varied depending on the substrate concentration, further supporting the contention that the reactions of manganese porphyrin complexes with peracids generate multiple reactive oxidizing intermediates.

An unsymmetrically π-extended porphyrin-based single-crystal field-effect transistor and its anisotropic carrier-transport behavior.

Anisotropic charge transport: Single-crystal organic field-effect transistor devices derived from aggregates of thiophene-appended porphyrins display very high mobility (0.27 cm(2) V(-1) s(-1)). This behavior is due to staircase stacking of the porphyrins with distances between layers of 3.17(7) Å. Furthermore, the charge-transport behavior is anisotropic owing to an anisotropic molecular arrangement in the single-crystal microplates.

Topographical Analysis of Pacinian Corpuscle in the Pulp of Human Cadaver Finger Tip Pulp: A Pilot Cadaver Study.

Background: The human hand is a specialised organ for fine motion and sensation and has a relatively large representation in the homunculus. The pathway of sensation starts from information sent by mechanoreceptors in the hand. This study reports the topography of the Pacinian corpuscle in the fingertips of a human cadaver. Methods: All 10 digits from both hands of a fresh-frozen cadaver were examined. Glabrous skin distal to the distal interphalangeal joint was harvested superficial to the periosteum including fat and subcutaneous tissue. The glabrous skin were divided into 10 sections that included five distal and five proximal sections. Modified gold chloride staining was performed. Sectioned specimens were observed under a light microscope and the density of Pacinian corpuscles was determined in each segment. The density of the corpuscles was compared between the radial/ulnar and proximal/distal segments and also between digits from the right hand versus those from the left hand. Results: Pacinian corpuscles were observed only in the subcutaneous tissue. There was no significant difference in density of the corpuscles between the distal and proximal segments or between the right and left hands. There was a statistically significant greater density of Pacinian corpuscles on the radial segments of all digits except the thumb. Conclusions: There is a greater density of Pacinian corpuscles on the radial side of the human fingertip in all digits except the thumb.

Photothermally Active Core-Shell Catalyst Based on UiO-66 and Polydopamine for Highly Effective Detoxification of Nerve Agents.

A new, photothermally active, catalytic composite (Fe3O4@PD@UiO-66) based on UiO-66 and polydopamine (PD) was prepared for the decomposition of chemical warfare agents (CWAs). An iron oxide nanoparticle was introduced to enable rapid recovery after the reaction. The PD layer enabled conversion of the absorbed light into heat under infrared (IR) irradiation and increased the reaction temperature, thereby increasing the reaction rate. Dendrimer-functionalized silica particles (NH2-DS) were used as heterogeneous catalyst regenerators instead of N-ethylmorpholine. Under IR irradiation, a mixture of Fe3O4@PD@UiO-66 and NH2-DS was effective as a heterogeneous catalyst for degrading DMNP, with a 5 min half-life in water. Without IR irradiation, the half-life of DMNP was 45 min using the same catalyst mixture. Various bases including arginine, histidine, and D4 were directly modified on the surface of Fe3O4@PD@UiO-66 and used without NH2-DS or N-ethylmorpholine in order to compare their reactivities. Furthermore, a mixture of Fe3O4@PD@UiO-66 and NH2-DS was used for the decomposition of nerve agents, including sarin (GB), soman (GD), and VX, under IR-LED irradiation. Remarkably, GB was effectively decomposed with a half-life of 4.2 min, and GD demonstrated a half-life of 8.7 min. VX was hydrolyzed with a half-life of 14.0 min.

Lysophosphatidic acid receptor 1 antagonist (EPGN2154) causes regression of NASH in preclinical NASH models.

BACKGROUND: NASH causes a tremendous health care burden in the United States. A glucagon-like peptide-1 agonist, semaglutide (Sema), treatment resulted in hepatic steatosis reduction in clinical trials of NASH. Lysophosphatidic acid receptor 1 antagonists are known to have antifibrotic effects in several organs. We tested Sema and a novel lysophosphatidic acid receptor 1 antagonist, EPGN2154, individually and in combination to evaluate their efficacy for NASH remission in preclinical models. METHODS: In the present study, we used (1) C57Bl6/J wild-type mice fed on a high-fat, high-carbohydrate (HFHC) diet for 16 weeks and (2) leptin-deficient mice (ob/ob) fed on an Amylin liver NASH diet for 16 weeks. After 16 weeks, the mice were randomly distributed in equal numbers in (1) no-drug, (2) EPGN2154, (3) Sema, and (4) EPGN2154+Sema treatment groups for 8 additional weeks at a dosage of 10 mg/kg body weight for EPGN2154 (oral gavage, 5 days a week) and 6.17 µg/kg body weight of Sema (subcutaneous injection every alternate day, 3 days a week). RESULTS: In the wild-type-high-fat, high-carbohydrate model, we observed the most body weight loss in the EPGN2154+Sema combination group compared to the other treatment groups. All groups led to a significant reduction in alanine transaminase levels when compared to high-fat, high-carbohydrate-fed wild type. However, no significant difference in alanine transaminase levels was observed among the treatment groups. In the ob/ob mice study, Sema did not cause body weight loss. Moreover, the EPGN2154 and the combination groups had a lower NAFLD Activity Score and incidence of advanced-stage hepatic fibrosis than the Sema group. CONCLUSIONS: EPGN2154 demonstrated a hepato-protective effect independent of body weight loss in preclinical NASH models.

Amide-based nonheme cobalt(III) olefin epoxidation catalyst: partition of multiple active oxidants Co(V)=O, Co(IV)=O, and Co(III)-OO(O)CR.

A mononuclear nonheme cobalt(III) complex of a tetradentate ligand containing two deprotonated amide moieties, [Co(bpc)Cl(2)][Et(4)N] (1; H(2)bpc = 4,5-dichloro-1,2-bis(2-pyridine-2-carboxamido)benzene), was prepared and then characterized by elemental analysis, IR, UV/Vis, and EPR spectroscopy, and X-ray crystallography. This nonheme Co(III) complex catalyzes olefin epoxidation upon treatment with meta-chloroperbenzoic acid. It is proposed that complex 1 shows partitioning between the heterolytic and homolytic cleavage of an O-O bond to afford Co(V)=O (3) and Co(IV)=O (4) intermediates, proposed to be responsible for the stereospecific olefin epoxidation and radical-type oxidations, respectively. Moreover, under extreme conditions, in which the concentration of an active substrate is very high, the Co-OOC(O)R (2) species is a possible reactive species for epoxidation. Furthermore, partitioning between heterolysis and homolysis of the O-O bond of the intermediate 2 might be very sensitive to the nature of the solvent, and the O-O bond of the Co-OOC(O)R species might proceed predominantly by heterolytic cleavage, even in the presence of small amounts of protic solvent, to produce a discrete Co(V) O intermediate as the dominant reactive species. Evidence for these multiple active oxidants was derived from product analysis, the use of peroxyphenylacetic acid as the peracid, and EPR measurements. The results suggest that a less accessible Co(V)=O moiety can form in a system in which the supporting chelate ligand comprises a mixture of neutral and anionic nitrogen donors.

N-doped porous carbons derived from Zn-porphyrin-MOF.

N-doped porous metal-organic framework (MOF)-derived carbons (MDCs) were directly synthesized from a new Zn-DpyDtolP-MOF (ZnDpyDtolP·1/2DMF, H2DpyDtolP = 5,15-di(4-pyridyl)-10,20-di(4-methylphenyl)porphyrin) containing a 3D hexagonal network through a self-templated carbonization method. KOH-activated MDC derivatives denoted as MDC-700-nKOH were also prepared with different weight ratios of KOH activator to MDC (MDC : KOH = 1 : n, where n = 1, 2). Compared to bare MDC, MDC-700-nKOH showed effective improvements of both gas sorption and electrochemical capacitive properties. More developed microporosity by KOH activation might induce great enhancement of high operating capacitive performances. The N-doped MDC-700-2KOH had high maximum gravimetric specific capacitance (555.6 F g-1) and specific energy (40.4 W h kg-1) at 0.1 A g-1 in 1 M H2SO4. Even at a high current density of 190 A g-1 in 6 M KOH, it exhibited high capacitive performance with a large specific power of 80 423 W kg-1. MDC-700-nKOH electrodes also showed good recycling properties of electrochemical capacitance up to 30 000 cycles.

Pullout strength of pedicle screws using cadaveric vertebrae with or without artificial demineralization.

OBJECTIVES: To evaluate the differences in the pullout strength and displacement of pedicle screws in cadaveric thoracolumbar vertebrae with or without artificial demineralization. METHODS: Five human lumbar and five thoracic vertebrae from one cadaver were divided into two hemivertebrae. The left-side specimens were included in the simulated osteopenic model group and the right-side bones in a control group. In the model group, we immersed each specimen in HCl (1 N) solution for 40 minutes. We measured bone mineral density (BMD) using dual-energy X-ray absorptiometry and quantitative computerized tomography. We inserted polyaxial pedicle screws into the 20 pedicles of the cadaveric lumbar and thoracic spine after measuring the BMD of the 2 hemivertebrae of each specimen. We measured the pullout strength and displacement of the screws before failure in each specimen using an Instron system. RESULTS: The average pullout strength of the simulated osteopenic model group was 76% that of the control group. In the control and model groups, the pullout strength was 1678.87±358.96 N and 1283.83±341.97 N, respectively, and the displacement was 2.07±0.34 mm and 2.65±0.50 mm, respectively (p<.05). We detected positive correlations between pullout strength and BMD in the control group and observed a negative correlation between displacement and BMD in the model group. CONCLUSIONS: By providing an anatomically symmetric counterpart, the human cadaveric model with or without demineralization can be used as a test bed for pullout tests of the spine. In the simulated osteopenic model group, pullout strength was significantly decreased compared with the untreated control group. CLINICAL SIGNIFICANCE: Decreased bone mineral density may significantly reduce the pullout strength of a pedicle screw, even though the range is osteopenic rather than osoteoporotic.

Spinal Stenosis Grading in Magnetic Resonance Imaging Using Deep Convolutional Neural Networks.

STUDY DESIGN: Retrospective magnetic resonance imaging grading with comparison between experts and deep convolutional neural networks (CNNs). OBJECTIVE: This study aims to verify the feasibility of a computer-assisted spine stenosis grading system by comparing the diagnostic agreement between two experts and the agreement between the experts and trained artificial CNN classifiers. SUMMARY OF BACKGROUND DATA: Spinal stenosis grading is important; however, it is tedious job to check the MR images slide by slide to classify patient grades often having different opinions regarding the final diagnosis. METHODS: For 542 L4-5 axial MR images, two experts independently localized the center position of the spine canal and graded the status. Two CNN classifiers each trained with the grading label made by the two experts were validated using 10-fold cross-validation. Each classifier consisted of a CNN detection model responsible for the localization of patches near the canal and a classification CNN model to predict the spinal stenosis status in the localized patches. Faster R-CNN was used for the detection model whereas VGG network was used for the classification model. A comparison in grading agreement was carried out between the two experts as well as that of the experts and the prediction results generated by the CNN models. RESULTS: Grading agreement between the experts was 77.5% and 75% in terms of accuracy and F1 scores. The agreement between the first expert and the model trained with the labels of the first expert was 83% and 75.4%, respectively. The agreement between the second expert and the model trained with the labels of the second expert was 77.9% and 74.9%. The differences between the two experts were significant, whereas the differences between each expert and the trained models were not significant. CONCLUSION: We indeed confirmed that automatic diagnosis using deep learning may be feasible for spinal stenosis grading. LEVEL OF EVIDENCE: 4.

Retained Foreign Body Which Should be Suspected as a Cause of Retractable Chronic Hand Inflammation and Diagnostic Capacity of Ultrasonography.

Background: Foreign bodies in the hand are common but easily and often missed in the initial evaluation of injury. Diagnosing retained foreign bodies is difficult due to radiolucent foreign bodies. Purpose of this study is to emphasize the need of consideration of foreign bodies in patients with chronic synovitis in hand. Methods: Twenty-five patients who had retained foreign body in soft tissue of hand with chronic inflammation symptoms were included. Ultrasonography was conducted in all of the patients. Patient age, sex, localization of foreign body, duration of symptom, history of injury, follow up period, complication, and biopsy results were recorded and reviewed. Also, patients' demographics and clinical results were retrospectively reviewed. Results: Nine of the 25 patients diagnosed with a foreign body in the hand did not remember the initial presentation of injury. The average symptom duration (from injury to hospitalization) was 10.5 months (range 1-96 months). The middle finger and the proximal interphalangeal joint were the most common site of a retained foreign body (10 patients). All patients were diagnosed via ultrasonography and underwent surgery. Biopsy results showed mainly chronic inflammation, fibrosis, granuloma, and foreign bodies. Conclusions: Patient with symptoms of cellulitis, osteomyelitis, and palpable mass in hand for over a month without a diagnosis should be suspected of retained FBs.

Chiral metallocycles: rational synthesis and novel applications.

Chiralsupramolecular systems have attracted a great deal of interest from synthetic chemists over the past two decades because of their ability to mimic complex biological processes and their potential applications in enantioselective events such as asymmetric catalysis and chiral sensing. Chiral metallocycles, among the simplest forms of chiral supramolecular systems, are of particular interest because of their relative ease of synthesis. In this Account, we survey recent developments in the rational design and synthesis of chiral metallocyclic systems based on metal-ligand coordination and their potential applications in enantioselective recognition and catalysis. General design principles for metallocycles are first introduced with particular focus on thermodynamic and kinetic considerations. The symmetry requirements for the linear and angular building units, the influence of stoichiometries and reaction concentrations, and the roles of solvents are discussed. Optimum synthetic conditions for the self-assembly and directed-assembly of metallocycles are also compared. Three synthetic strategies for chiral metallocycles are broadly categorized based on the source of chirality, namely, (1) introduction of metallocorners containing chiral capping groups, (2) use of metal-based chirality owing to specific coordination arrangements, and (3) introduction of chiral bridging ligands. The bulk of this Account focuses on the third synthetic strategy with examples of chiral metallocycles built from atropisomeric bridging ligands based on the 1,1'-binaphthalene framework. The influences of ligand geometries and metallocorner configurations on the metallocycle structures are demonstrated. The synthetic utility of directed-assembly processes is illustrated with numerous examples of cyclic polygons ranging from nanoscopic dimers to a mesoscopic 47mer. Moreover, the directed-assembly processes offer exquisite control on structure, chirality, and functionality of the metallocycles. A number of interesting applications have been demonstrated with chiral metallocycles with diverse sizes and functionalities. For example, metallocycles with the Pt(diimine) metallocorners show interesting behaviors as luminophores in prototype light-emitting devices, chiral molecular squares based on 1,1'-binaphthyl-derived bipyridyl bridging ligands and fac-ReCO3Cl corners exhibit enantioselective luminescence in the presence of the 2-amino-1-propanol analyte, and chiral metallocycles based on 1,1'-binaphthyl-derived bialkynyl bridging ligands and cis-PtPEt2 corners activate Ti(IV) centers to catalyze highly enantioselective diethylzinc additions to aromatic aldehydes to afford chiral secondary alcohols. Additionally, chiral metallocycles synthesized via the weak-link approach (WLA) are shown to exhibit allosteric regulation. They experience significant changes in the cavity sizes and shapes upon the introduction of other ligands, with the resulting open structures serving as a catalyst for acyl transfer reaction or as an enantioselective recognition pocket. In summary, chiral metallocycles with much enhanced stability, favorable solubility characteristics, unprecedentedly large sizes, well-positioned functional groups, and desired chirality have been synthesized using a combination of self- and directed-assembly strategies. The applications of these chiral metallocycles in light-emitting devices, allosteric regulation, chiral sensing, and asymmetric catalysis have been demonstrated. The examples illustrated in this Account give testimony to chemists' ability, through chemical manipulations, to create large and complex chiral metallocycles that can potentially serve as mimics of natural enzyme systems.

Probing exciton localization/delocalization: transient dc photoconductivity studies of excited states of symmetrical porphyrin monomers, oligomers, and supramolecular assemblies.

Solution-phase transient dc photoconductivity (TDCP) measurements are used to address the question of exciton localization/delocalization in strongly coupled oligomeric porphyrins and in well-defined, higher-order assemblies of oligomers (ladder and prism assemblies). The approach used is determination of the excited-state excess polarizability volume, Delta alpha(V)--a quantity known to report on exciton delocalization. The measurements reveal for the oligomers that singlet excitons are substantially delocalized but that triplet excitons are much more localized. For each of the two higher-order assemblies, the measurements reveal that excitons are transiently confined to individual oligomeric subunits rather than being delocalized over the entire assembly.

Neuroanatomical distribution of sensory receptors in the human elbow joint capsule.

BACKGROUND: The topographic arrangement of sensory receptors in the human elbow joint capsule is pertinent to their role in the transmission of neural signals. The signals from stimuli in the joint are concisely delivered via afferent pathways to allow recognition of pain and proprioception. Sensory receptors in the elbow joint include mechanoreceptors and free nerve endings acting as nociceptors, although the distribution of each of the structures has not been determined, despite their importance for the integrity of the joint. We therefore aimed to investigate the neuroanatomical distribution and densities of mechanoreceptors and free nerve endings in the capsule of the elbow, at the same time as considering surgical approaches that would result in the minimum insult to them. METHODS: Four elbow joint capsules were harvested from fresh cadavers. The specimens were carefully separated from adjacent osteoligamentous attachments and the capsular complex was stained with a modified gold chloride method. Evaluations of free nerve endings, and Golgi, Ruffini and Pacinian corpuscles were performed under an inverted light microscope. The number and density of each structure were recorded. RESULTS: Ruffini corpuscles observed to be the dominant mechanoreceptor type. No Golgi corpuscle was observed. Free nerve endings were found at the highest density at posterodistal sites, whereas mechanoreceptors were most frequent at bony attachment sites. CONCLUSIONS: A consistent distribution pattern of articular sensory receptors was observed, which allows further understanding of elbow pathology. An awareness of the neuroanatomical distribution of sensory receptors in the elbow joint capsule may allow their preservation during surgical procedures for elbow joint pathology.

Modified Transosseous Wiring Technique for Neglected Fracture-Dislocation of the Proximal Interphalangeal Joint.

BACKGROUND: Fracture-dislocation of the proximal interphalangeal (PIP) joint of the finger is challenging due to the high risk of stiffness. The purpose of this study is to evaluate the clinical and radiological results of a modified transosseous wiring technique for the management of chronic fracture-dislocations of the PIP joint. METHODS: Ten patients (nine men and one woman; mean age, 38.3 years; range, 21 to 69 years) with neglected fracture-dislocation of the PIP joint were included. The mean duration from injury to operation was 14.7 weeks (range, 3 to 66 weeks). The dorsolateral approach and extension block pinning were used to reduce dislocation. After thorough debridement of the scar tissues in the dorsal dead space and the fracture site, the reduction was maintained with transosseous wiring. Radiologic evaluations of bone union and arthritic changes and clinical evaluations (range of motion of the PIP joint and Disabilities of the Arm, Shoulder and Hand [DASH] score) were performed. The mean follow-up period was 12.9 months (range, 12 to 19 months). RESULTS: All patients demonstrated evidence of radiographic healing within a mean healing time of 6 weeks (range, 4 to 10 weeks); however, one had a widened gap and one had an early arthritic change. The mean range of motion in the PIP joint was 81° (range, 50° to 105°). The mean DASH score was 21.6 (range, 7.5 to 35.8). CONCLUSIONS: For chronic fracture-dislocation of the PIP joint, transosseous wiring with direct curettage and optimal bone purchase can provide satisfying outcome.

Growth of narrowly dispersed porphyrin nanowires and their hierarchical assembly into macroscopic columns.

The self-assembly of amphiphilic (porphyrin)Sn 1 in an aqueous Pluronic F127 media results in the formation of narrowly dispersed nanowires. Variation of aqueous Pluronic concentrations allows for a systematic variation of porphyrin nanowire lengths while keeping their widths constant. These nanowires can be further assembled into secondary macroscopic columns.

Cavity-tailored, self-sorting supramolecular catalytic boxes for selective oxidation.

Using a steric self-sorting strategy, the assembly of highly ordered and rigid supramolecular boxes possessing catalytic properties has been achieved in one step. The formation of these assemblies, comprising up to 18 porphyrin centers, was readily confirmed by solution X-ray scattering in conjunction with fluorescent spectroscopy. Size-selective and enantioselective oxidation catalysis were both demonstrated.

Coordinative self-assembly and solution-phase X-ray structural characterization of cavity-tailored porphyrin boxes.

Combining linear Zn porphyrin trimers with orthogonally derivatized porphyrin dimers leads rapidly and spontaneously to the formation of monodisperse, torsionally constrained boxes comprising six components and a total of 16 metalloporphyrins. In situ X-ray scattering measurements confirm the formation of monodisperse assemblies of precisely the size expected from model box structures. While simple subunits yield highly symmetrical boxes, we find that sterically demanding subunits produce unusual twisted boxes. Previous studies of porphyrin-based box-like assemblies (squares) for selective catalysis and molecular sieving revealed two function-inhibiting structural problems: torsional motion along the metal-porphyrin-metal axis and ambiguous outside versus inside functionalization (via axial ligation of available Zn(II) sites). The new 16-porphyrin box assemblies eliminate both problems.

Intramolecular energy transfer within butadiyne-linked chlorophyll and porphyrin dimer-faced, self-assembled prisms.

The synthesis and photophysical properties of butadiyne-linked chlorophyll and porphyrin dimers in toluene solution and in several self-assembled prismatic structures are described. The butadiyne linkage between the 20-positions of the macrocycles results in new electronic transitions polarized along the long axes of the dimers. These transitions greatly increase the ability of these dimers to absorb the solar spectrum over a broad wavelength range. Femtosecond transient absorption spectroscopy reveals the relative rate of rotation of the macrocycles around the butadiyne bond joining them. Following addition of 3-fold symmetric, metal-coordinating ligands, both macrocyclic dimers self-assemble into prismatic structures in which the dimers comprise the faces of the prisms. These structures were confirmed by small-angle X-ray scattering experiments in solution using a synchrotron source. Photoexcitation of the prismatic assemblies reveals that efficient, through-space energy transfer occurs between the macrocyclic dimers within the prisms. The distance dependence of energy transfer between the faces of the prisms was observed by varying the size of the prismatic assemblies through the use of 3-fold symmetric ligands having arms with different lengths. These results show that self-assembly of discrete macrocyclic prisms provides a useful new strategy for controlling singlet exciton flow in antenna systems for artificial photosynthesis and solar cell applications.