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A novel class of four-connecting three-dimensional molecular 2-5 based on biaryls for supramoelcular self-assembly is synthesized. The X-ray crystal structure analysis of tetraphenol with ethanol reveals a novel O-H...O hydrogen-bonded helical self-assembly in three dimensions leading to the generation of channels in the crystal lattice.

The synthesis, structure, and magnetic properties of two new tetranuclear Cu(II) complexes containing N,N,N',N'- tetraethylpyridine-2,6-dithiocarboxamide (S-dept) of formula [Cu2Cl2(mu-S-dept)2]Cu2Cl4(mu-Cl)2] and [Cu2(mu-Cl)2-(S-dept)2][CuCl3(EtOH)]2 are reported. Their X-ray crystal structures reveal that the complexes are composed of anionic and cationic dimers.

Research has been conducted on Cu (sub)2 (mu-Cl) (sub)2 Cl (sub)2 (L) (sub)2] (L= dialkylpyridine-2,6-dicarboxylate) complexes. The preparation of these complexes, their crystal structure and magnetic properties have been investigated, and the details are reported.

Research conducted on the diorganotin oxides to investigate dimethyl sulfite behavior toward organotin nucleophilic reagents is analyzed. Results demonstrate organotin compound-mediated rearrangement at sulfur center.

The designed and application of tetraarylpyrenes H1-H4 that typify molecular systems with orthogonal planes and lack hydrogen bonding functional groups as new host systems with three distinct domains for guest inclusion is reported. The unique features of H1-H4 facilitated binding of the aliphatic and aromatic small-size guest molecules such as CH[Cl.sub.3], [(C[H.sub.3]).sub.2]S, etc. in the basin domain while aliphatic and aromatic guests in the channel/concave and trough regions, respectively.

The (E)-photoenols generated in situ by photolysis of o-tolualdehydes in the solid state react with the precursor aldehydes as dienophiles in a hetero-Diels-Alder cycloaddition fashion to afford trans-3-arylisochromanols in excellent yields and in a high diastereoselectivity. The results observed with o-tolualdehydes exemplify successful execution of tandem reactions in the solid state.

We have explored O–H···Ohydrogen bonded self-assembly of rigid three-connecting mesitylenetribenzoicacid (H3MTB). Thetriacid is shown to exploit the acid dimer motif and self-assemble,in the solid state, into a 6-fold interpenetrated (6,3) honeycombnet with the pores of the dimension of ca. 24–26 Å. Itis shown that crystallization of H3MTBwith K+/NH4+salts in the presence of 18-crown-6 leads to mono-deprotonationfollowed by self-assembly of the resultant H2MTB–into multicomponentcrystals of different network structures sustained by charge-assistedhydrogen bonds. The X-ray crystal structure analyses reveal that thesolvent employed to access the multicomponent crystals plays the roleof a chaperon in modifying the supramolecular structures adopted.Crystallization of H3MTBin the presence of dibenzo-18-crown-6 is found to lead likewiseto a (6,3) net that is 6-fold interpenetrated with K+⊂dibenzo-18-crown-6occupying the voids. Thus, the strategy involving partial deprotonationof rationally designed polycarboxylic acids with KX/crown is shownto lead to multicomponent crystals sustained by charge-assisted hydrogenbonds. The structural studies have led to identification of water-mediatedpaddlewheel and carboxylate···carboxylate dimer synthons. [ABSTRACT FROM AUTHOR]

The diastereomers of ketones 2 and 3 are shown to exhibit distinct photochemical reactivities due to conformational preferences; while the anti isomers of 2 and 3 undergo efficient Yang cyclization in 75-90% yields with a remarkable diastereoselectivity (> 90%), the syn isomers predominantly undergo Norrish Type II elimination. The differences in the product profiles of the diastereomers are consistent with a mechanistic picture involving the formation of precursor diastereomeric triplet 1,4-biradicals in which the substituents at α and β-positions stabilize the cisoid (cyclization) or transoid (elimination) geometry. The fact that such a diastereomeric relationship does indeed ensue at the triplet-excited-state itself is demonstrated via the nanosecond laser-flash photolysis of model ketones 1. The diastereomeric discrimination in the product profiles observed for ketones 2 and 3 as well as in the triplet lifetimes observed for ketones 1 can both be mechanistically traced back to different conformational preferences of the ground-state diastereomeric ketones and the intermediary 1,4-biradicals. Additionally, it emerges from the present study that the syn and anti diastereomers of ketones 2 and 3 represent two extremes of a broad range of widely examined butyrophenones, which lead to varying degrees of Yang photocyclization depending on the alkyl substitution pattern. [ABSTRACT FROM AUTHOR]

Over the last 50 years, proposals of α-carbonyl cation intermediates have been driven by chemical intuition and indirect evidence. Recently, wide interest in α-carbonyl cation chemistry has opened new gates to prepare α-functionalized carbonyl compounds. Though these intrinsically unstable carbocations are formed under forcing conditions (e.g., in a strong acid medium), their fleeting existence prohibits direct observation or spectroscopic measurement. We report that high-speed aqueous microdroplets can directly capture α-carbonyl cation intermediates from various reactions (Friedel-Crafts arylation, deoxygenation, and azidation) upon bombarding with the corresponding reaction aliquots. The α-carbonyl cations caged in water droplets are then desorbed to the gas phase, allowing their successful measurement by mass spectrometry. This has also enabled us to simultaneously monitor the relative abundance of the associated precursor, α-carbonyl cation intermediate, and product during the progress of the reaction.

The complexes [Cu2(mu-Cl)2(Cl)2(L)2] (L = dialkylpyridine-2,6-dicarboxylate; R = Et, L = depc, 1; R = i-Pr, L = dppc, 2) have been prepared and their magnetic properties studied. The crystal structures of complexes 1 and 2 have been solved. Compound 1 belongs to the P space group with Z = 2, a = 8.3020(10) A, b = 9.2050(10) A, c = 10.065(2) A, alpha = 99.040(10), beta = 100.810(10), and gamma = 106.502(10) whereas 2 belongs to the C2/c space group with Z = 8, a = 11.6360(10) A, b = 25.906(3) A, c = 11.76579(10) A, and beta = 107.900(10). The different alkyl ester substitutes produce substantial structural and electronic differences. The Cu2Cl2 core geometry is planar for 1 whereas it adopts a butterfly shape in the case of 2. Furthermore, in 2 the dppc ligand coordinates only by the carbonyl oxygen atoms whereas in 1 the depc ligand coordinates through carbonyl and alkoxy oxygen atoms. Magnetic susceptibility data show a ferromagnetic coupling between the two Cu(II) centers in both cases (J = 39.9(6) cm(-1) for 1, and J = 51.3(5) cm(-1) for 2) with very weak antiferromagnetic interactions (J ' = -0.59 cm(-1) and -0.57 cm(-1) for 1 and 2, respectively). Theoretical calculations at the extended Hückel level have also been carried out to further understand the electronic nature of complexes 1 and 2.

One-pot reactions of diorganotin oxides, R(2)SnO, with dimethyl sulfite under reflux conditions (125-127 degrees C) proceed via the Arbuzov rearrangement at the sulfur center, yielding the corresponding methoxydiorganotin methanesulfonates, R(2)Sn(OMe)OS(O)(2)Me [R = n-Pr (1), n-Bu (2), i-Bu (3), c-Hx (4)], as white, hygroscopic solids. These compounds react with beta-diketones [acetylacetone (Hacac), benzoylacetone (Hbzac), and dibenzoylmethane (Hbzbz)] to afford mixed-ligand organotin derivatives, R(2)Sn(X)OS(O)(2)Me [X = acac, R = n-Pr (5), n-Bu (6); X = bzac, R = n-Pr (7), n-Bu (8); X = bzbz, R = n-Pr (9), n-Bu (10), i-Bu (11)]. Selective hydrolysis of the Sn-OMe bond in 1-3 occurs, resulting in the isolation of (&mgr;-hydroxo)diorganotin methanesulfonates, R(2)Sn(OH)OS(O)(2)Me [R = n-Pr (12), n-Bu (13), i-Bu (14)]. All the compounds are characterized by elemental analyses and IR, multinuclear ((1)H, (13)C, and (119)Sn) NMR, and mass spectra. Unequivocal evidence of the presence of the methanesulfonate group is provided by the X-ray crystal structures of 6, 10, and 13. [For 6: trigonal space group R&thremacr; (No. 148), a = 28.664(1) Å, c = 13.056(1)Å, Z = 18. For 10: triclinic space group P&onemacr; (No. 2), a = 13.056(3) Å, b = 14.062(3) Å, c = 16.282(3) Å, Z = 4. For 13: triclinic space group P&onemacr; (No. 2), a = 9.089(2) Å, b = 12.040(2) Å, c =13.894(2) Å, Z = 2]. For 6 and 10, the solid-state structural analyses reveal dimeric structures with a bridging bidentate methanesulfonate group forming a centrosymmetric eight-membered ring. Compound 13 possesses a polymeric sheet structure with repeating 20-membered macrocycles (including two four-membered [Sn(OH)](2) rings) by virtue of the bridging bidentate methanesulfonate groups. A search for a possible pathway to give Arbuzov-rearranged products 1-4 leads us to speculate that there is an initial catalytic transformation of dimethyl sulfite to methyl methanesulfonate via intermediate compounds, Bu(2)Sn(OMe)(2) (A) and [Bu(2)SnOMe](2)O (B). A and B subsequently react with methyl methanesulfonate to give 1-4.