Studies in the cycloproparene series: cycloaddition reactions of diarylmethylidenecycloproparenes

Journal ArticleDiarylmethylidenecyclopropanaphthalenes 4b-d add diphenylisobenzofuran (DPIBF) and α-pyrone across the exocyclic double bond to give ring expanded products 11b-d and 13b-d that result from subsequent relief of ring strain in the non-isolable spirocyclic intermediates 10 and 12, respectively. The benzene homologues 3b and 3c add DPIBF across the bridge bond to give the norcaradiene adducts 19b and 19c

One-dimensional coordination polymers based on first-row transition metals: a solid-state study of weak backbone interactions

Journal ArticleWe present further data on the solid-state structures of one-dimensional coordination polymers based upon dipositive transition metal hexafluoroacetylacetonate (hfacac) complexes. A variety of linking subunits are employed in order to investigate and probe the relatively weak interactions that make up the backbones of these polymers. Reported in this study are metal complexes containing manganese, zinc, copper, and cobalt and a range of donor building blocks encompassing an array of bonding motifs, including pyridyl-metal, pyridyl(N-oxide)-metal, and hydrogen bonding. The specific linkers utilized are 4,4′-dipyridyl N,N′- dioxide hydrate, 2,5-bis(4-ethynylpyridyl)furan, 4,4′-trimethylenedipyridine, and trans-1-(2-pyridyl)-2-(4-pyridyl)-ethylene. A detailed discussion of the products is presented, as is a comparison to known compounds of a similar nature. All compounds are characterized via single-crystal X-ray diffraction and elemental analysis for the bulk of the sample

Self-selected formation of single discrete supramolecules with flexible, bidentate ligands in the coordination-driven self-assembly

Journal ArticleFlexible donor ligands like 1,2-bis(3-pyridyl)ethyne or 1,4-bis(3-pyridyl)-1,3-butadiyne selfassemble into discrete 2-D supramolecules instead of infinite networks upon combination with organoplatinum 90, 120, and 180 degree acceptor units. These systems are unique examples of versatile pyridine donors adjusting their bonding directionality to accommodate rigid platinum acceptors in the formation of closed macrocycles. Discrete, nanoscopic 3-D cages are also prepared in high yield via coordination-driven self-assembly from bidentate 3-substituted pyridines and tripod organoplatinum acceptors. Flexible, bidentate 3-substituted pyridine donors and a rigid organopalladium acceptor are also exclusively selfassembled into discrete 2-D macrocycles. Moreover, discrete supramolecules are successfully prepared from ambidentate donor ligands and platinum containing acceptors. Despite the possibility of forming more than one product, ambidentate ligands prefer to self-assemble predominantly into one species. Flexible, ambidentate pyridyl-carboxylate based donor ligands like sodium 3-(3-pyridyl)benzoate, sodium 4-(3-pyridyl)benzoate and potassium 4-(3-pyridyl)ethynylbenzoate self-assemble into discrete [2+2] macrocyclic species instead of infinite networks when combined with a 90 degree organoplatinum acceptor. In each case only one isomeric ensemble is selectively formed in high yield. All products are characterized by electrospray ionization mass spectrometry (ESI-MS), 31P{1H} and 1H NMR spectroscopy. They are the first examples of discrete supramolecules incorporating flexible, bidentate donor ligands. Despite their potential versatility, these flexible donors adjust their bonding directionality to accommodate a rigid acceptor in the formation of one discrete ensemble

Self-assembly of coordinative supramolecular polygons with open binding sites

ManuscriptThe design and synthesis of coordinative supramolecular polygons with open binding sites is described. Coordination-driven self-assembly of 2,6-bis(pyridin-4-ylethynyl)pyridine with 60? and 120? organoplatinum acceptors results in quantitative formation of a supramolecular rhomboid and hexagon, respectively, both bearing open pyridyl binding sites. The structures were determined by multinuclear (31P and 1H) NMR spectroscopy and electrospray ionization (ESI) mass spectrometry, along with a computational study

Supramolecular chemistry and molecular design: self-assembly of molecular squares

Journal ArticleModem supramolecular chemistry has been described as organized polymolecular systems held together by noncovalent interactions and represents one of the major frontiers in the chemical sciences.'-' At present the field is dominated by the hydrogen bonding motif that mimics biological systems and the classical covalent macrocyclics such as crown ethers, cyclophanes, cyclodextrins, calixarenes, etc., that represent the roots of the field!?' Much less is known about the use of coordination and transition metals as a motif for the assembly of supramolecular species

Incorporation of flexible pyridine-functionalized ligands into discrete supramolecules via coordination-driven self-assembly

Journal ArticleFlexible, pyridine-functionalized ligands were self-assembled into discrete supramolecules of differing stoichiometries upon combination with various organoplatinum molecules. They are characterized by electrospray ionization mass spectrometry, 31P(iHI and 'H NMR. Despite its inherent flexibility, 3-substituted pyridines 1 and di-pynrdyl substituted 18-membered diaza-crown ligand 8 prefer to self-assemble into closed systems when reacted with platinum-containing acceptors

Concentration-dependent supramolecular patterns of C3 and C2 symmetric molecules at the solid/liquid interface

Here we report on a scanning tunnelling microscopy (STM) investigation on the self-assembly of C3- and C2-symmetric molecules at the solution/graphite interface. 1,3,5-tris((E)-2-(pyridin-4-yl)vinyl)benzene and 1,1,2,2-tetrakis(4-(pyridin-4-yl)phenyl)ethane are used as model systems. These molecules displayed a concentration dependent self-assembly behaviour on graphite, resulting in highly ordered supramolecular structures, which are stabilized jointly by van der Waals substrate-adsorbate interactions and in-plane intermolecular H-bonding. Denser packing is obtained when applying a relatively high concentration solution to the basal plane of the surface whereas a less dense porous network is observed upon lowering the concentration. We show that the molecular conformation does not influence the stability of the self-assembly and a twisted molecule can pack into dense and porous architectures under the concentration effect

How well can post‐traumatic stress disorder be predicted from pre‐trauma risk factors? An exploratory study in the WHO World Mental Health Surveys

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/108700/1/wps20150.pd

Single-molecule level control of host-guest interactions in metallocycle-C60 complexes

Host−guest interactions are of central importance in many biological and chemical processes. However, the investigation of the formation and decomplexation of host−guest systems at the single-molecule level has been a challenging task. Here we show that the single-molecule conductance of organoplatinum(II) metallocycle hosts can be enhanced by an order of magnitude by the incorporation of a C60 guest molecule. Mechanically stretching the metallocycle-C60 junction with a scanning tunneling microscopy break junction technique causes the release of the C60 guest from the metallocycle, and consequently the conductance switches back to the free-host level. Metallocycle hosts with different shapes and cavity sizes show different degrees of flexibility to accommodate the C60 guest in response to mechanical stretching. DFT calculations provide further insights into the electronic structures and charge transport properties of the molecular junctions based on metallocycles and the metallocycle-C60 complexes

Man of Letters, Literary Lady, Journalist or Reporter?

The enormous changes wrought in the British newspaper industry during the late nineteenth and early twentieth centuries brought about a revolution in newspaper reading habits, financing and influence, all aspects of which have been well-documented by historians of the press. But what of the contributor, particularly the freelance whose millions of words formed, mostly anonymously, the content of the new mass market press? How did writers negotiate changes in the literary marketplace during this time as editors demanded more ‘news’ and less in the way of whimsical paragraphing, and sketches, the traditional newspaper output of the professional man, or woman, of letters? Through the study of memoirs, correspondence and the fictional output of contributors to the press during this time, it is possible to discern the often fraught relations between writers and their most lucrative market