Two-dimensional amine and hydroxy functionalized fused aromatic covalent organic framework

Ordered two-dimensional covalent organic frameworks (COFs) have generally been synthesized using reversible reactions. It has been difficult to synthesize a similar degree of ordered COFs using irreversible reactions. Developing COFs with a fused aromatic ring system via an irreversible reaction is highly desirable but has remained a significant challenge. Here we demonstrate a COF that can be synthesized from organic building blocks via irreversible condensation (aromatization). The as-synthesized robust fused aromatic COF (F-COF) exhibits high crystallinity. Its lattice structure is characterized by scanning tunneling microscopy and X-ray diffraction pattern. Because of its fused aromatic ring system, the F-COF structure possesses high physiochemical stability, due to the absence of hydrolysable weak covalent bonds

Phylogeny and Taxonomy of the Round-Eared Sengis or Elephant-Shrews, Genus Macroscelides (Mammalia, Afrotheria, Macroscelidea)

The round-eared sengis or elephant-shrews (genus Macroscelides) exhibit striking pelage variation throughout their ranges. Over ten taxonomic names have been proposed to describe this variation, but currently only two taxa are recognized (M. proboscideus proboscideus and M. p. flavicaudatus). Here, we review the taxonomic history of Macroscelides, and we use data on the geographic distribution, morphology, and mitochondrial DNA sequence to evaluate the current taxonomy. Our data support only two taxa that correspond to the currently recognized subspecies M. p. proboscideus and M. p. flavicaudatus. Mitochondrial haplotypes of these two taxa are reciprocally monophyletic with over 13% uncorrected sequence divergence between them. PCA analysis of 14 morphological characters (mostly cranial) grouped the two taxa into non-overlapping clusters, and body mass alone is a relatively reliable distinguishing character throughout much of Macroscelides range. Although fieldworkers were unable to find sympatric populations, the two taxa were found within 50 km of each other, and genetic analysis showed no evidence of gene flow. Based upon corroborating genetic data, morphological data, near sympatry with no evidence of gene flow, and differences in habitat use, we elevate these two forms to full species

SPECTROSCOPIC INVESTIGATION OF ELECTRON-INDUCED PROTON TRANSFER IN THE FORMIC ACID DIMER, (HCOOH)2_{2}

Author Institution: Yale University, Department of Chemistry, New Haven, CTWe have isolated the stable form of the formic acid dimer anion (HCOOH)$_{2}^{-}$, a model for electron-induced proton transfer between nucleic acid base-pairs, in the gas phase. The vibrational signatures of this species and its various isotopomers were investigated using Ar predissociation and photodetachment spectroscopies in the 600-3800 \wn\ range. We relate the experimental infrared transitions of the anion to those predicted for its calculated lowest energy structure in order to determine if a proton transfer event does in fact occur upon excess electron attachment to this simple hydrogen-bonded dimer. Additionally, we determined its vertical detachment energy (VDE), 1.8 eV, using velocity-map photoelectron imaging

USING AN ORGANIC SCAFFOLD TO MODULATE THE QUANTUM STRUCTURE OF AN INTRAMOLECULAR PROTON BOND: CRYOGENIC VIBRATIONAL PREDISSOCIATION SPECTROSCOPY OF H2_{2} ON PROTONATED 8-NAPHTHALENE-1-AMINE

Author Institution: Sterling Chemistry, Yale University, New Haven, Ct, 06520; DEPARTMENT OF CHEMISTRY, JOHNS HOPKINS UNIVERSITY, 3400 NORTH CHARLES STREET, BALTIMORE, MD, 21218The quantum structure of the intermolecular proton bond is a key aspect in understanding proton transfer events that govern the efficiency of fuel cells and various biological membranes. Previously, we have constructed a soft binding motif, that consists of a "point contact" between the lone pairs of two small molecules (combinations of ethers, alcohols, ammonia, and water) that are linked by a shared proton [\textit{Science} 2007, \textit{613}, 249]. Although the frequency of the shared proton vibration has been correlated with effects of acid and base structure, such as proton affinities and dipole moments, the spatial arrangement of the proton donor and acceptor remains unexplored. Towards this aim, we have obtained a molecule of rigid topology that contains a proton donor and acceptor capable of intramolecular proton-bonding (protonated 8-flouronaphthalene-1-amine). Using electrospray ionization coupled with a novel cryogenic mass spectrometry scheme, we employ vibrational predissociation spectroscopy of H$_{2}$ tagged ions to elucidate how a forced spatial configuration of the acid and base perturbs the energetics of the proton bond

"PROTON SPONGES": A RIGID ORGANIC SCAFFOLD TO REVEAL THE QUANTUM STRUCTURE OF THE INTRAMOLECULAR PROTON BOND

Author Institution: Yale University, P. O. Box 208107, New Haven, CT, 06520; Johns Hopkins University, 3400 North Charles Street, Baltimore, MD, 21218; Brock University, St. Catherines, ON, Canada L2S 3A1Spectroscopic analysis of systems containing charged hydrogen bonds (e.g. the Zundel ion, $\mathrm{H}_{5}\mathrm{O}_{2}^{+}$) in a vibrationally cold regime is useful in decongesting numerous anharmonic features common to room temperature measurements.[Roscioli, J. R.; et. al. Science 2007] This approach has been extended to conjugate acids of the "Proton Sponge" family of organic compounds, which contain strong intramolecular hydrogen bonds between proton donor (D) and acceptor (A) groups at the 1- and 8-positions. By performing $\mathrm{H}_2/\mathrm{D}_2$ vibrational predissociation spectroscopy on cryogenically cooled ions, we explore how the proximity and spatial orientation of D and A moieties relates to the spectroscopic signature of the shared proton. In the cases studied ($\mathrm{D = Me_{2}N-H^{+}; A = OH, O(C=O)Ph}$), we observe strong anharmonic couplings between the shared proton and dark states that persist at these cryogenic temperatures. This leads to intense NH stretching features throughout the nominal CH stretching region ($2800-3000 \mathrm{cm}^{-1}$). Isotopic substitution has verified that the oscillator strength of these broad features is driven by NH stretching. Furthermore, the study of A = O(C=O)Ph has provided a spectroscopic snapshot of the shared proton at work as an active catalytic moiety fostering ester hydrolysis by first order acylium fission ($\mathrm{A_{AC}1}$). This is apparent by the high frequency carbonyl stretch at $1792\ \mathrm{cm}^{-1}$, which is a consequence of the strong hydrogen bond to the ether-ester oxygen atom. Thus, these "Proton Sponges" are useful model systems that unearth the quantum structure and reactivity of shared proton interactions in organic compounds