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Adam J Matzger

Publications and source records attributed to Adam J Matzger.

26 records · Page 2Linked to original sources
PubMed2003

Comparison of "polynaphthalenes" prepared by two mechanistically distinct routes.

The Bergman cyclization has long been known to produce polymers as side products. More recently, this attribute has been harnessed for the production of conjugated materials. However, the structures of these polymers have not been established. To resolve this question, the metal-catalyzed polymerization of 1,4-dibromonaphthalene and thermal polymerization of o-diethynylbenzene were conducted. Two distinct polymers were obtained. Comparison of IR spectroscopy, MALDI-TOF MS, solid-state NMR spectroscopy, UV-vis reflectance spectroscopy, and pyrolysis GC-MS data indicates that only one of the polymers is consistent with poly(1,4-naphthalene).

Journal Article↗
PubMed2003

Computation of aromatic C3N4 networks and synthesis of the molecular precursor N(C3N3)3Cl6.

The successful synthesis and structural characterization of molecules that represent segments of extended solids is a valuable strategy for learning metric and stereochemical characteristics of those solids. This approach has been useful in cases in which the solids are particularly difficult to crystallize and thus their atomic connectivity and overall structures become difficult to deduce with X-ray diffraction techniques. One such class of materials is the covalently linked C(x)N(y) extended solids, where molecular analogues remain largely absent. In particular, structures of C(3)N(4) solids are controversial. This report illustrates the utility of a simple molecule, N(C(3)N(3))(3)Cl(6), in answering the question of whether triazine based C(3)N(4) phases are layered or instead they adopt 3D structures. Here, we present density functional calculations that clearly demonstrate the lower stability of graphitic C(3)N(4) relative to 3D analogues.

Journal Article↗
PubMed2003

Photochemistry of diethynyl sulfides: a cycloaromatization for the formation of five-membered rings.

The first five-membered ring cycloaromatization reaction has been demonstrated. Photoirradiation of bis(phenylethynyl) sulfide in hexanes/1,4-cyclohexadiene produces 3,4-diphenylthiophene through the presumed intermediacy of 2,5-didehydrothiophene. In addition, phenylacetylene is produced in this reaction consistent with competing direct carbon-sulfur cleavage. For reactions in ethanol or 2-propanol production of the thiophene is accompanied by the formation of phenylacetylene and a thionoester of the corresponding alcohol. Thiophene products also result from the irradiation of other diethynyl sulfides. [reaction: see text]

Journal Article↗
PubMed2003

Comparison of the four anhydrous polymorphs of carbamazepine and the crystal structure of form I.

For decades, carbamazepine (CBZ) has served as a model compound for groups engaged in the study of crystal polymorphism. Despite considerable effort, crystal structures for only three of its four anhydrous forms have previously been determined. Herein, we report the first single crystal X-ray structure of the high temperature modification of CBZ (form I). Form I crystallizes in a triclinic cell (P-1) having four inequivalent molecules with the following lattice parameters: a = 5.1705(6), b = 20.574(2), c = 22.245(2) A, alpha = 84.12(4), beta = 88.01(4), and gamma = 85.19(4) degrees. Furthermore, we compare the physical properties of the four anhydrous polymorphs of CBZ, including the first comprehensive characterization of form IV. Substantial differences are seen among these forms by powder X-ray diffraction, infrared spectroscopy, thermomicroscopy, and differential scanning calorimetry. These data are correlated to their respective crystal structures for the first time. We have found that all polymorphs possess identical strong hydrogen bonding patterns, similar molecular conformations, and stabilities that are within 0.7 kcal/mol of each other.

Calorimetry, Differential Scanning↗
PubMed2002

The use of polymer heteronuclei for crystalline polymorph selection.

A method for the production of crystalline polymorphs from solution is described which utilizes a diverse set of polymer heteronuclei. Application to crystalline polymorph selection for the important pharmaceuticals acetaminophen and carbamazepine is demonstrated. This method provides a new paradigm for polymorph selection, where solvent and temperature conditions can be chosen on the basis of process considerations and the polymer heteronucleus can be varied for specific polymorph production.

Journal Article↗
PubMed2002

Inequivalent molecules in a two-dimensional crystal.

Physisorbed monolayers formed at solution-solid interfaces are two-dimensional crystals sharing many structural characteristics, such as packing motifs and reactivity, with their three-dimensional counterparts. Study of these monolayers with scanning tunneling microscopy (STM) offers a promising tool for exploring crystallization phenomena. Although the analogy between the structures of two-dimensional and three-dimensional crystals is becoming clearer with the imaging of increasing numbers of molecules with STM, the occurrence of inequivalent molecules in a unit cell has been limited to three-dimensional crystals. We report that the monolayer of 1,3-dinonadecanoyl benzene formed at the solution-HOPG interface possesses a unit cell with 1.5 inequivalent molecules (Z' = 1.5) demonstrating that, as in the case of three-dimensional crystals, simple molecules can give rise to inequivalent packing in the solid state.

Journal Article↗
PubMed2002

Form IV of carbamazepine.

Carbamazepine has been found to crystallize as a new polymorph that is stable at room temperature. We report the crystal structure of this C-centered monoclinic form (space group C2/c, cell parameters: a = 26.609, b = 6.9269, c = 13.957, beta = 109.702), which consists of hydrogen bonded dimers with an anti-disposition. This represents the third modification of carbamazepine that has been crystallographically characterized, and the fourth for which cell parameters have been determined. Thus, it is designated as form IV of carbamazepine. Differences between the packing of the various polymorphs are discussed.

Anticonvulsants↗