1.Tuning chloride binding, encapsulation, and transport by peripheral substitution of pseudopeptidic tripodal small cages.
Martí I1, Rubio J, Bolte M, Burguete MI, Vicent C, Quesada R, Alfonso I, Luis SV. Chemistry. 2012 Dec 21;18(52):16728-41. doi: 10.1002/chem.201202182. Epub 2012 Nov 13.
A highly efficient synthesis of small pseudopeptidic cages from simple precursors has been achieved by the triple S(N)2 reaction between tripodal tris(amido amines) and several 1,3,5-tris(bromomethyl)benzene electrophiles. The success of the macrobicyclization strongly depends on the central triamine scaffold, which dictates the correct preorganization of the intermediates. The chloride binding properties of the protonated pseudopeptidic cages have been studied in the solid state (by X-ray diffraction) as well as in solution (by NMR spectroscopy and ESI-MS) and in the gas phase (by collision-induced dissociation (CID)-MS). The crystal structure of the HCl salts of several cages show a chloride partially or completely caged within the cavity of the macrobicycle. Both the amino acid side chain and the substitution at the aromatic tripodal ring have an effect on the chloride binding ability. The cages derived from the 1,3,5-benzene moiety show low affinity, whereas the triple substitution in the ring (either with Me or Et) increases the chloride binding by one order of magnitude.
2.Synthesis, Characterization, and Electrochemistry of Heterometallic Dendrimers.
Achar S1, Immoos CE, Hill MG, Catalano VJ. Inorg Chem. 1997 May 21;36(11):2314-2320.
A method for the synthesis of new heterometallic dendritic molecules containing organoplatinum centers is reported. Reaction of Pt(2)Me(4)(&mgr;-SMe(2))(2) with bpy-Fc(2) (1) (bpy-Fc(2) = 4,4'-bis(ferrocenylvinyl)-2,2'-bipyridine) gave the platinum(II) complex PtMe(2)(bpy-Fc(2)) (2). Complex 2 undergoes oxidative addition with iodomethane to yield PtMe(3)I(bpy-Fc(2)) (3) and with bis(bromomethyl)benzenes to yield complexes of the type [PtMe(2)Br(bpy-Fc(2))CH(2)-](2)R (4, R = 1,2-C(6)H(4); 5, R = 1,3-C(6)H(4); 6, R = 1,4-C(6)H(4)). 1, 3, and 4 were characterized by X-ray structure determinations. For 1, a = 11.780(3) Å, b = 10.662(3) Å, c = 11.642(3) Å, beta = 118.61(2) degrees, and V = 1283.7(6) Å(3) while, for 2, a = 11.497(2) Å, b = 22.796(6) Å, c = 15.801(3) Å, beta = 106.08(1) degrees, and V = 3979(2) Å(3). Only poor quality crystals of 4 could be obtained resulting in a partial structure refinement with a = 14.46(1) Å, b = 15.14(1) Å, c = 21.
3.Sterically congested in-methylcyclophanes.
Song Q1, Ho DM, Pascal RA Jr. J Am Chem Soc. 2005 Aug 17;127(32):11246-7.
The crowded in-methylcyclophane 9 was prepared by condensation of 1,8,13-tris(bromomethyl)-9-methyltriptycene and 1,3,5-tris(mercaptomethyl)benzene under high dilution conditions. Oxidation of 9 gave the highly crystalline trisulfone 10, and its X-ray structure was determined. The in-methyl carbon atoms of the two independent molecules in the structure are only 2.90 and 2.87 A from the centroid of the basal aromatic ring, the closest such contacts ever observed. In addition, the C-CH3 bonds in these cyclophanes are compressed; the two independent bond distances are 1.475 and 1.495 A, significantly shorter than the ca. 1.54 A distances found in similar but uncongested molecules.
Fernandes JA1, Vilela SM, Ribeiro-Claro PJ, Almeida Paz FA. Acta Crystallogr C. 2011 Jun;67(Pt 6):o198-200. doi: 10.1107/S0108270111013618. Epub 2011 May 5.
The asymmetric unit of the title compound, C(9)H(9)Br(3), is composed of a single molecule. Two bromo substituents are located on one side of the plane of the aromatic ring and the third is on the opposite side, with the molecular unit exhibiting an approximate noncrystallographic C(s) point group. The crystal structure is rich in Br...Br, CH(2)···Br and CH···π weak intermolecular contacts which mediate the crystal packing of individual molecules. These interactions promote a red-shift of a handful of vibrational modes (associated with the pendant -CH(2)Br groups) compared with values from theoretical density functional theory (DFT) calculations.