Marcia L. Scudder

Bio: Marcia L. Scudder is an academic researcher from University of New South Wales. The author has contributed to research in topics: Crystal structure & Diol. The author has an hindex of 37, co-authored 224 publications receiving 4870 citations.

Supramolecular Motifs: Concerted Multiple Phenyl Embraces between Ph4P+ Cations Are Attractive and Ubiquitous

Abstract: Examination of the Cambridge Structural Database reveals that Ph4P+ cations in crystals associate through phenyl-phenyl nonbonded interactions which are attractive, concerted, and widespread. Intermolecular phenyl-phenyl conformations, which are offset-face-to-face (off), edge-to-face (ef) or vertex-to face (vf), combine in five classes of supramolecular motifs for {Ph4P+}2 pairs, namely the sextuple phenyl embrace (SPE) with (ef)6 and offset sextuple phenyl embrace (OSPE) containing (off)1 (ef)2(ef/vf)2, the translational quadruple phenyl embrace (TQPE) with (ef)4, the parallel quadruple phenyl embrace (PQPE) with (off)1(vf)2, and the double phenyl embrace (DPE) with (off)1. Typical intermolecular attractive energies (kJ per mol of {Ph4P+}2) for these motifs are SPE 85, OSPE 57, TQPE 70, PQPE 41, DPE 34. There is strong interpenetration of the cations in these motifs: 489/770 structures in the CSD have P P≤7 A (spherical Ph4P+ has a van der Waals diameter of 13.6 A). Of the 812 instances of P P ≤7 A, 86% are SPE, 10% are OSPE, 2% are TQPE, and only 2% are unclassified, Average P P separations in the PQPE and DPE are 8.3 A. Centrosymmetry is prevalent in all except the TQPE, which has implications for the engineering of noncentric crystals.

Layered structure of crystalline compounds silver thiolates (AgSR)

Abstract: The insoluble silver thiolate compounds AgS(CH 2 ) 2 CH 3 (1), AgS(CH 2 ) 3 CH 3 (2), AgS(CH 2 ) 5 CH 3 (3), AgS(CH 2 ) 7 CH 3 (4), AgSC 6 H 5 (5), AgSC 6 H 4 -4-F (6), AgSC 6 H 4 -4-Cl (7), AgSC 6 H 4 -4-Br (8), AgSC 6 H 4 -4-CH 3 (9) and AgSC 6 H 4 -4-OCH 3 (10) have not yielded crystals suitable for full diffraction analysis, but do reveal the essential features of their two-dimensionally nonmolecular structure in their powder diffraction patterns

[S4Cd17(SPh)28]2-, the first member of a third series of tetrahedral [SWMX(SR)y]z- clusters

Abstract: Le compose du titre cristallise dans le systeme orthorhombique avec le groupe d'espace Ccca et sa structure est affinee jusqu'a 0,059

The crystal supramolecularity of metal phenanthroline complexes

Abstract: The 1,10-phenanthroline (phen) ligand in metal complexes commonly forms offset face-to-face (OFF) motifs, and less frequently edge-to-face (EF) motifs. An investigation of the 335 M(phen) complexes, 159 M(phen)2 complexes, and 33 M(phen)3 complexes in the Cambridge Structural Database has revealed that in crystals these primary OFF and EF motifs combine to form concerted motifs, and extended motifs, in a variety of ways. Stacks of phen ligands engaging OFF motifs on both faces are very common for complexes M(phen) and M(phen)2. Even more common for M(phen)2 are zigzag chains in which each phen ligand links to neighbours in the chain with an OFF motif. The parallel fourfold aryl embrace (P4AE, comprised of one OFF and two EF) occurs for complexes M(phen)2 and M(phen)3, with some variety in geometry between a single OFF at one extreme to (EF)2 at the other. This variability in the P4AE is a consequence of the larger surface area of the phen ligand, compared with those of 2,2′-bipyridyl (bipy) ligands or phenyl groups (which also form this motif), and has been evaluated by calculations of the supramolecular attractive energies. The P4AE associate further, maximising the use of phen surfaces, to form chains of P4AE, chains of P4AE·OFF, and compact two-dimensional nets propagated by both P4AE and OFF motifs. There are examples of three-dimensional nets using these motifs. There is a notable absence of sixfold aryl embraces (6AE, comprised of concerted (EF)6) amongst M(phen)3 complexes, and a clear difference with M(bipy)3 complexes where 6AEs are prevalent. Various M(phen)2 and M(phen)3 complexes pack in crystals to form tight hydrophobic domains, often as slabs, segregated from hydrophilic domains containing hydrogen bonding components and anions. The crystallisation and crystal packing of [Co(phen)3][BF4]2·H2O·EtOH, which exemplifies this pattern, are reported. The implications for crystal engineered enantioselection by [M(phen)3] complexes are discussed.

Molecular self-assembly and nanochemistry: A chemical strategy for the synthesis of nanostructures

Abstract: Molecular self-assembly is the spontaneous association of molecules under equilibrium conditions into stable, structurally well-defined aggregates joined by noncovalent bonds. Molecular self-assembly is ubiquitous in biological systems and underlies the formation of a wide variety of complex biological structures. Understanding self-assembly and the associated noncovalent interactions that connect complementary interacting molecular surfaces in biological aggregates is a central concern in structural biochemistry. Self-assembly is also emerging as a new strategy in chemical synthesis, with the potential of generating nonbiological structures with dimensions of 1 to 10(2) nanometers (with molecular weights of 10(4) to 10(10) daltons). Structures in the upper part of this range of sizes are presently inaccessible through chemical synthesis, and the ability to prepare them would open a route to structures comparable in size (and perhaps complementary in function) to those that can be prepared by microlithography and other techniques of microfabrication.

Self-Organization of CdSe Nanocrystallites into Three-Dimensional Quantum Dot Superlattices

Abstract: The self-organization of CdSe nanocrystallites into three-dimensional semiconductor quantum dot superlattices (colloidal crystals) is demonstrated. The size and spacing of the dots within the superlattice are controlled with near atomic precision. This control is a result of synthetic advances that provide CdSe nanocrystallites that are monodisperse within the limit of atomic roughness. The methodology is not limited to semiconductor quantum dots but provides general procedures for the preparation and characterization of ordered structures of nanocrystallites from a variety of materials.

The chemistry and antioxidant properties of tocopherols and tocotrienols

Abstract: This article is a review of the fundamental chemistry of the tocopherols and tocotrienols relevant to their antioxidant action. Despite the general agreement that α-tocopherol is the most efficient antioxidant and vitamin E homologuein vivo, there was always a considerable discrepancy in its “absolute” and “relative” antioxidant effectivenessin vitro, especially when compared to γ-tocopherol. Many chemical, physical, biochemical, physicochemical, and other factors seem responsible for the observed discrepancy between the relative antioxidant potencies of the tocopherolsin vivo andin vitro. This paper aims at highlighting some possible reasons for the observed differences between the tocopherols (α-, β-, γ-, and δ-) in relation to their interactions with the important chemical species involved in lipid peroxidation, specifically trace metal ions, singlet oxygen, nitrogen oxides, and antioxidant synergists. Although literature reports related to the chemistry of the tocotrienols are quite meager, they also were included in the discussion in virtue of their structural and functional resemblance to the tocopherols.