Honeycomb Architecture Research Articles

Supramolecular Reactivity of Porphyrins with Mixed Iodophenyl and Pyridyl meso-Substituents

This study evaluates the supramolecular reactivity of the 5-(4′-pyridyl)-10,15,20-tris(4′-iodophenyl)porphyrin (PyTIPP) and 5,15-bis(4′-pyridyl)-10,20-bis(4′-iodophenyl)porphyrin (PyDIPP) platforms in their free base and metalated forms, utilizing metal–ligand coordination and halogen bond synthons in the construction of polymeric as well as oligomeric assemblies. Free base PyTIPP and PyDIPP moieties form extended supramolecular layers held together by intermolecular N···I and I···π interactions, which π···π stack in an offset manner to yield layered crystals. The metalated monopyridyl derivative Co-PyTIPP (as well as its Zn-PyTIPP analogue) assembles into cyclic tetrameric supermolecule via coordination of the pyridyl function of one species to the core metal ion of an adjacent unit. On the other hand, the bis-pyridyl Zn-PyDIPP scaffold constructs a robust framework solid of extended honeycomb architecture by polymeric self-coordination. These findings provide useful protocols for rational design of the different modes of supramolecular porphyrin ensembles, which are valid in reaction media lacking polar reagents with competing affinity for the functional groups of the porphyrin units. In the latter context, PyDIPP in the presence of benzoic acid forms discrete solvated entities, where the pyridyl N-sites engage in hydrogen bonds to the carboxylic acids, preventing direct inter-porphyrin association.

Rational design of a new class of heterobimetallic molecule-based magnets: Synthesis, crystal structures, and magnetic properties of oxamato-bridged [formula omitted] (M′ = Li I and Mn II; M = Ni II and Co II) open-frameworks with a three-dimensional honeycomb architecture

Two new series of oxamato-bridged heterobimetallic coordination networks of general formula Li 5[Li 3M 2(mpba) 3(H 2O) 6] · 31H 2O [M = Ni II ( 1a) and Co II ( 1b)] and Li 2[Mn 3M 2(mpba) 3(H 2O) 6] · 22H 2O [M = Ni II ( 2a) and Co II ( 2b)] have been prepared from the metal-mediated self-assembly of the hexakis(bidentate), triple-stranded dinickel(II) and dicobalt(II) complexes [M 2(mpba) 3] 8− [mpba = meta-phenylenebis(oxamato)] with either monovalent lithium(I) or divalent manganese(II) ions respectively, in water. X-ray structural analyses of 1a and 1b show an anionic three-dimensional network formed by an infinite parallel array of oxamato-bridged Li 3 I M 2 II (M = Ni and Co) hexagonal layers, which are interconnected through three m-phenylenediamidate bridges between the M II ions of opposite propeller chirality ( Δ and Λ) to give dinuclear metallacryptand cores of the meso-helicate-type. The intralayer Li–M distance through the oxamate bridge is 5.380(3) ( 1a) and 5.396(5) ( 1b) Å, while the interlayer M–M distance through the triple m-phenylenediamidate bridge is 6.856(3) ( 1a) and 6.851(3) ( 1b) Å. Overall, this leads to an open-framework honeycomb structure with large hexagonal pores of ca. 21.8 ( 1a) and 21.5 Å ( 1b) in diameter which are occupied by linear arrays of water-bridged Li I countercations. Variable-temperature (2.0–300 K) dc magnetic susceptibility and variable-field (0–5.0 T) magnetization measurements on these two series of compounds reveal a distinct magnetic behavior mainly depending on the diamagnetic or paramagnetic nature of the Li I and Mn II ions, respectively. Compounds 1a and 1b behave as rather well-isolated M 2 II (M = Ni and Co) dimers with a moderate to weak ferromagnetic coupling ( J Ni–Ni = +3.17 cm −1 and J Co–Co = +1.03 cm −1) between the two M II ions across the triple m-phenylenediamidate bridge, together with either an appreciable to remarkable local ion axial magnetic anisotropy ( D Ni = −3.35 cm −1) or spin–orbit coupling ( λ Co = −167.3 cm −1); the next nearest-neighbor magnetic interactions between the M II ions through the diamagnetic Li I ions are negligible. Compounds 2a and 2b behave instead as strongly coupled oxamato-bridged Mn 3 II M 2 II (M = Ni and Co) ferrimagnetic planes which are weakly interacting through the m-phenylenediamidate bridges, leading thus to a long-range 3D ferromagnetic order at T C = 6.5 K. In addition, the variable-temperature (2.0–12 K) ac magnetic susceptibility measurements on 2a and 2b show an intriguing frequency-dependent magnetic behavior characteristic of a spin-glass dynamics. This glassy behavior is likely attributed to their amorphous character and/or the moderate to strong magnetic anisotropy of the dinickel(II) and dicobalt(II) precursors.

Preparation and Structure of Three Solvatomorphs of the Polymer [Co(dbm)2(4ptz)]n: Spin Canting Depending on the Supramolecular Organization

The syntheses and X-ray structures of three isomeric 1D coordination polymers are reported. The complex [Co(dbm)2(MeOH)2] (1) was used as a precursor in these reactions. The preparation and structure of 1 is also presented; this mononuclear complex is in the cis configuration because this allows the formation of a network of intermolecular hydrogen bonds in the solid state. Reaction of 1 with 2,4,6-tris-(4-pyridyl)-1,3,5-triazine (4ptz) yields the polymers [Co(dbm)2(4ptz)]n.nTHF (2a), [Co(dbm)2(4ptz)]n.0.75nTHF.0.5nEt2O (2b), and [Co(dbm)2(4ptz)]n.3nDMF (2c) in the form of zigzag chains, instead of the expected honeycomb architectures. This is because of the establishment of extended pi-pi stacking throughout these solids, which could not have occurred otherwise. Compounds 2a, 2b, and 2c are solvatomorphs, and formation of either one of them depends on the exact conditions of crystallization, which lead to significant differences in the supramolecular organization of the chains. Bulk magnetic measurements on 2a reveal weak antiferromagnetic exchange within the chains and small ordering throughout the solid that results in the manifestation of the phenomenon of spin canting, whereas for 2c the different supramolecular organization causes the antiferromagnetic exchange not to result in spin canting.

Porous 3-D honeycomb architecture by self-assembly of helical H-bonded molecular tapes

Enantiopure dipeptide-derived 1,3,5-triazepan-2,6-diones and form H-bonded 3(1) helical molecular tapes with P chirality in the solid state; in the case of , these columnar tapes self-assemble through aromatic-aromatic interactions to give hollow tubular structures.

Multimodal in vivo optical imaging, including confocal microscopy, facilitates presurgical margin mapping for clinically complex lentigo maligna melanoma

Knowledge of the accurate margins of a lentigo maligna melanoma (LMM) is crucial in the presurgical evaluation of the patient. Towards this end clinicians have utilized the Wood's lamp and dermoscopy to help delineate the borders of the LMM. However, many LMMs arise on photodamaged skin, making it difficult to determine the border of the LMM and separate it from the background lentiginous skin. We present a case of a patient with a recurrent LMM on the scalp that developed in a background of photodamage with diffuse melanocytic atypia and lentigines, making it virtually impossible to determine the precise margins of the LMM by clinical, Wood's lamp or dermoscopic examination. To avoid subjecting the patient to multiple staged excisions we attempted to determine the margins of the LMM by utilizing in vivo confocal laser scanning reflectance microscopy. Using this, it was apparent that there were increased numbers of atypical/dendritic intraepidermal melanocytes in all layers of the epidermis within the LMM. In contrast, skin not involved with the LMM, as viewed under confocal laser examination, had normal honeycomb architecture and no abnormal melanocytes. The confocally determined border was further confirmed by obtaining multiple punch biopsies that were evaluated by haematoxylin and eosin histology and immunohistochemistry. Based on this information, the presurgical margins were marked and the tumour excised accordingly. The excised tissue was examined with multiple-step sections and the margins were determined to be clear. There has been no evidence of tumour recurrence after 1 year. In conclusion, this case illustrates that confocal reflectance microscopy, in conjunction with other in vivo optical instruments, can be utilized to enhance the accuracy for the presurgical margin mapping of LMM.

5,10,15,20-Tetrakis(4-pyridyl)porphyrinato]zinc(II) acetic acid clathrate, and its unique polymeric honeycomb architecture

The crystal structure of the title compound, [Zn(C40H24N8)]·1.6C2H4O2 has been determined at ca 110 K. The centrosymmetric metalloporphyrin compound forms a self-assembled honeycomb architecture, with open channels extending parallel to the c axis of the unit cell. The compound crystallizes as an acetic acid clathrate. The guest species, which are included in the inter­porphyrin channels, hydrogen bond to the porphyrin framework.

Polyoxometalate-Based Vesicle and Its Honeycomb Architectures on Solid Surfaces

The introduction of cationic surfactant DODA as counterions of [Eu(H2O)2SiW11O39]5- can form a mesoscopic supramolecular assembly of (DODA)4H[Eu(H2O)2SiW11O39], which aggregates into vesicles in chloroform. This POM-based vesicle can be further transferred into three-dimensional microporous architectures under moist air. The present methodology shows that, by combining inorganic chemistry and colloidal surface chemistry, a sequential self-assembling approach based on a series of linkable preorganized building blocks allows access to the fabrication of technological applicably POM-based microsized patterns, alternated with the soft lithographic method.

Supramolecular synthesis of brick wall and honeycomb networks from the T-shaped molecule 5-nitrosalicylic acid

The T-geometry of O–H⋯O and C–H⋯O hydrogen bonding groups in the title molecule (5-NSA) form a brick wall network that is modularly expanded and transformed to chair cyclohexane and honeycomb architectures in molecular complexes with trans-1,4-dithiane-1,4-dioxide and dioxane. The variation in hydrogen bond synthons results in different examples of topologically related (6,3) nets.

A Study in Crystal Engineering: Structure, Crystal Growth, and Physical Properties of a Polar Perhydrotriphenylene Inclusion Compound

Racemic perhydrotriphenylene (PHTP) forms a polar inclusion compound with 1-(4-nitrophenyl)piperazine (NPP) as a guest molecule. Homochiral stacks of PHTP molecules surround polar chains of hydrogen-bonded NPP molecules in a channel-type, honeycomb architecture. The NPP chains are arranged in an all-parallel (rather than an antiparallel) fashion. Crystals of [PHTP]5[NPP] show second harmonic generation for incident light of wavelength 1064 nm, an electro-optical and a pyroelectric effect. The X-ray diffraction pattern exhibits Bragg-like reflections, interspersed with planes of diffuse scattering and weak satellite reflections superimposed on these planes, features which are indicative of extensive disorder. In spite of this, an orthorhombic average structure model could be deduced from the Bragg-like reflections (space group Cmc21, a = 15.023(2), b = 23.198(2), and c = 4.730(1) Å (T = 100 K), wR2 = 0.088, goodness of fit 1.38). A qualitative interpretation of diffuse and satelite scattering is given. Crystals of [PHTP]5[NPP] are approximately hexagonal prisms. If the tailor-made additive 1-(p-tolyl)piperazine (TP) is present during crystallization, the habit changes to approximately hexagonal plates and TP is incorporated in small amounts. Crystals of the composition [PHTP]5[NPP]0.93[TP]0.07 lose the ability of second harmonic generation. The observation of polar properties for a crystal structure whose polar building blocks, the -NO2···HN- hydrogen-bonded NPP chains, are 14−15 Å apart and separated by PHTP hydrocarbon molecules is surprising, but can be explained in terms of a Markov chain model of crystal growth. The same simple model accounts for the loss of polarity in the presence of the tailor-made additive TP. The knowledge gained during the present analysis provides a rational tool for the engineering of polar properties of PHTP and similar channel-type inclusion compounds.

Fabrication of hollow porous shells of calcium carbonate from self-organizing media

A RICH variety of elaborate microscopic skeletal structures composed of inorganic materials are produced in nature1. Such complex, three-dimensional structures, if produced synthetically, could find important applications as light-weight ceramics, catalyst supports, biomedical implants and robust membranes for high-temperature separation technology. Here we describe a method for synthesizing hollow porous shells of crystalline calcium carbonate (aragonite) that resemble the coccospheres of certain marine algae. We show that thin cellular frameworks of either mesoporous or macroporous aragonite can be formed from oil–water–surfactant microemulsions supersaturated with calcium bicarbonate, with the pore size determined by the relative concentrations of water and oil. Using micrometre-sized polystyrene beads as the substrate for the microemulsion, hollow spherical shells of the honeycomb architecture can be produced. We propose that these cellular frameworks originate from rapid mineralization of aragonite, with a self-organized foam of oil droplets acting as a structural template, and suggest that similar processes could be of general importance in materials chemistry.

Mapping of neural networks on the honeycomb architecture

The use of the Honeycomb architecture for the implementation of neural networks in the next generation of supercomputers is discussed. The major point is that the relative value of various neural network models depends heavily on the chosen implementation technology. Models that are superior when it comes to conventional implementation architectures and related technologies may be inferior if the Honeycomb architecture and related technologies are used, and vice versa.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Experimental brain tumors and edema in rats. I. Histology and cytology of tumors.

In this study an experimental intracerebral tumor has been investigated with special consideration of structures, which may be involved in edema production and/or resolution. For this purpose a cloned tumor cell line (RG1 2.2) has been injected stereotactically into the brain of BD-IX rats. The tumor has some characteristics in common with low differentiated oligodendroglioma in men. A honeycomb architecture may be seen in the center of the tumor. It is built up by rounded or elongated cells, which can be impregnated in parts. In the central area, cells exhibit a voluminous digestive apparatus, composed of dictyosomes, vesicles, and some vacuoles with a membranaceous or homogeneous content. Tumor cells in the periphery show large processes and a small digestive apparatus. The sinusoidal tumor vessels are composed of an endothelium with many vesicles but no openings.