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The reactions of group 4 metals (Ti, Zr, and Hf) and 2,5-dihydroxyterephthalic acid (H4dobdc) under solvothermal conditions have been systematically explored, and their major crystalline phases have been investigated by single-crystal diffractions. Ti(IV) forms a layered framework [Ti2(Hdobdc)3] where honeycomb-type sheets are interconnected through strong hydrogen bonding. Various gases are reversibly adsorbed within the straight one-dimensional channels decorated with polar O atoms, and H2 and CO2 show relatively high isosteric heats of adsorption at 6.6 and 29.4 kJ/mol, respectively. Zr(IV)- and Hf(IV)-based MOFs have also been synthesized using the same ligand and are isostructural with the formula (H3O) x [M(dobdc)(bz) x ] (M = Zr or Hf). They have a unique, nonoxo-trinuclear building block that forms a polyhedral network of 6-connected topology. Unlike the two-dimensional net of Ti, the Zr and Hf metal-organic frameworks are hydrothermally stable as unambiguously shown by variable-temperature X-ray diffraction. [ABSTRACT FROM AUTHOR]

We have demonstrated a triangular assembly driven by 12 charged hydrogen bonds and π-π interactions. This assembly is stable even in polar solvents because of its charged hydrogen-bond nature. Helical arrangement of the complex is confirmed by its crystal structure. A solution structure is assigned to the D3 isomer corresponding to the solid-state structure by temperature-dependent ¹H NMR experiments. [ABSTRACT FROM AUTHOR]

By modulating the secondary building units derived from the primary building units, N-acylsalicylhydrazides (H3xshz), we have been able to construct isostructural but tunable host networks, [Mn6(xshz)6(dmf)2(bpea)2], with different cavity sizes and shapes where the secondary building units, [Mn6(xshz)6], were linked through exo-bidentate bridging ligand, 1,2-bis(pyridyl)ethane (bpea) to form 3-D networks. With a short length linear N-acyl side chain at the primary building unit, the host networks have a 3-D network with three-dimensional cavities. With an appropriate length linear N-acyl side chain at the primary building unit, the host network keeps the isostructural 3-D network but with two types of one-dimensional channels of reduced cavity volume. The tuned host networks showed not only size selectivity for the guest molecules but also shape selectivity. While the three-dimensional channeled host showed selectivity depending on the length of the podal guests, the one-dimensional channeled host showed selectivity depending on both the length and/or the podality of the guest molecules. [ABSTRACT FROM AUTHOR]

By using the tripodal tetradentate ligand tris(2-benzimidazolylmethyl)amine (H[sub 3]ntb), which can have several charge states depending on the number of secondary amine protons, mononuclear octahedral and dinuclear trigonal bipyramidal Fe(lll) complexes were prepared. The reaction of mononuclear octahedral [Fe[sup III](H[sub 3]ntb)Cl[sub 2]]ClO[sub 4], 1, with 3 equiv of sec-butylamine in methanol led to the formation of mononuclear cis-dimethoxo octahedral Fe[sup III](H[sub 2]ntb)(OMe)[sub 2], 2. One equivalent of the sec-butylamine was used to generate the monoanionic H[sub 2]ntb[sup -] ligand where one of the three amines in the benzimidazolyl groups was deprotonated. The remaining 2 equiv were used to generate two methoxides that were coordinated to the octahedral Fe(lll) ion in a cis fashion as demonstrated by the chlorides in 1. Reaction of 1 with excess (7 equiv) sec-butylamine generated the doubly deprotonated dianionic Hntb[sup 2-] that stabilized the dinudear μ-oxo Fe[sup III][sub 2]O(Hntb)[sub 2], 3, adopting a five-coordinate trigonal bipyramidal geometry. The magnetic data for 3 are consistent with the antiferromagnetically coupled Fe[sup III] (S = 5/2) sites with the coupling constant J = -127 cm[sup -1]. [ABSTRACT FROM AUTHOR]

A novel S4-symmetric icosanuclear manganese metalladiazamacrocycle was synthesized using a pentadentate ligand, N-3-phenyl- trans-2-propenoylsalicylhydrazide (H3L), that has a rigid and bulky terminal N-acyl group. A 20 cyclic repeat of an -(Mn-N-N)- linkage resulted in a highly puckered diaza-bridged 60-membered icosanuclear metallamacrocycle. The steric interaction between the ligands in the cyclic system leads to five consecutive MnIII centers in a chemically different -(MnAMnBMnCMnDMnE)- environment, with the chiralities of the metal centers being in a rather complicated -(ΛΛΔΛΛ)(ΔΔΛΔΔ)- sequence. [ABSTRACT FROM AUTHOR]

We report on helical coordination networks that were prepared using a hexanuclear manganese metallamacrocycle as a helical tecton. We were able to prepare the three-dimensional helical coordination networks using a hexanuclear manganese metallamacrocycle, [Mn6(Ishz)6], as a helical tecton, where N-lauroyl salicylhydrazide (H3lshz) was used as the primary building unit to generate the helical tecton as a secondary building unit. While the 41/43 screw symmetry-linked helical coordination network was obtained when the primary building units had an N-acetyl group, both the 31/32 screw symmetry-linked and the 41/43 screw symmetry-linked helical coordination networks were obtained simultaneously in the same batch when the primary building unit had a long alkyl N-lauroyl group at the N-acetyl site. [ABSTRACT FROM AUTHOR]

The article examines the utilization of the C3-symmetric facial ligands and C4-symmetric metal ions for the preparation of truncated octahedral nanocages. The curvature needed for truncation at the octahedral vertices was accomplished using ligands with a tilted pyridyl group and a nitrogen donor atom. The nanocages have 12 ports at the edges of the truncated octahedron.

Discrete metal-organic polyhedra (MOP) with nanosized cavities and/or clusters of MOP could be prepared when C3-symmetric facial ligands and a potential hexatopic Cu(II) ion are combined in the presence of perchlorate as a weak linker, while similar reaction conditions in the presence of a nitrate linker led to extended metal-organic frameworks made of MOP as supramolecular building blocks. [ABSTRACT FROM AUTHOR]

A three-dimensional Mn(II) framework, [Mn2(H2L)(L)0.5(MeOH)(DEF)]·0.1MeOH·0.1DEF·1.4H2O (1; H4L = 2,3-dioxido-1,4-benzenedicarboxylic acid), was synthesized under solvothermal conditions in diethylformamide/methanol (DEF/MeOH), where the Mn centers adopt octahedral and unusual pentagonal bipyramidal geometries. The ligand H4L was subject to deprotonation to create μ4-H2L2– and μ6-L4– anionic bridges, leading to the construction of a coordination network. The MeOH exchange process of crystalline 1 allowed for another crystalline phase (1a), which reversibly returned to the original crystalline state upon resolvation in DEF/MeOH. After evacuation of 1a, the amorphous phase 1b was irreversibly formed, followed by the restoration of the original phase 1 upon resolvation in DEF/MeOH. Consequently, this framework underwent cyclic structural transformations from the crystalline (1) to crystalline (1a) to amorphous (1b) and back to crystalline (1) phase, which are unique transformations for soft coordination networks. Magnetic measurements demonstrated that antiferromagnetic interactions were operative between the Mn(II) ions and were effectively mediated by the oxygen moieties of the μ6-L4– bridge. [ABSTRACT FROM AUTHOR]

A new palladium-catalyzed asymmetric addition reaction of indoles to alkoxyallenes is reported. Remarkably, the reaction showed complete regioselectivity toward the nitrogen. A new mechanism distinct from that of conventional π-allyl chemistry is proposed to explain this unique selectivity. The utility of the reaction is demonstrated by highly efficient and flexible synthesis of N-glycosylindoles. [ABSTRACT FROM AUTHOR]

Calix[n]triazoles are developed as new derivatives in the calixarene family. Calixtriazole compounds 2-4 are synthesized using an iterative convergent strategy including an inter-/intramolecular copper(I)-catalyzed azide-alkyne cycloaddition reaction. Solid-state structures are clearly refined to give 1,2-alternate and partial cone conformations for calix[4]triazole and calix[5]triazole, respectively. Theoretical studies based on density functional theory (DFT) calculations indicated that intermolecular interactions are crucial in determining the conformers of the crystals, and the most stable conformers of calix[4]triazole, calix[5]triazole, and calix[6]triazole in the monomeric forms are 1,3-alternate, 1,3-alternate, and 1,3,5-alternate, respectively. [ABSTRACT FROM AUTHOR]

Non-interpenetrated three-dimensional (3D) metal-organic frameworks (MOFs) with both an interpenetration-favorable (3,5)-c hms topology and an interpenetration-unfavorable (3,5)-c gra topology are converted to doubly interpenetrated analogues with hms-c topology by thermal treatment, even in the absence of solvent. Depending on the conversion temperature and the properties of the pillaring ligand in the non-interpenetrated 3D MOF, which is based on two-dimensional sheets with 3-c hcb topology pillared by neutral ditopic linkers, the pillaring ligands in the interpenetrated MOFs produced are partially removed during the thermal conversions, leading to interpenetrated MOFs that simultaneously contain both micro- and mesopores. [ABSTRACT FROM AUTHOR]

Triphenylamine (TPA), a propeller-shaped optoelectronic molecule, has been used to generate stimuli-responsive smart fluorescent organic materials and correlate the effect of subtle structural changes on the molecular packing and mechanochromic fluorescence (MCF). The substituent (OCH3) position in the TPA phenyl ring and acceptors (malononitrile, cyanoacetamide, cyanoacetic acid, ethyl cyanoacetate, and diethylmalonate) strongly influenced the solid state and mechanochromic fluorescence as well as the molecular packing. The structure-property studies revealed that (i) TPA derivatives without the OCH3 substituent exhibit strong fluorescence (ϕf = 85% (TCAAD-1, 55% (TDEM)), (ii) higher dihedral angle (τ) between donor (aminophenyl) and acceptor lead to weak/non fluorescent material, (iii) substituent at the ortho position to acceptor increased the dihedral angle (τ = 26.49 (TCAAD-2), τ = 27.14 (TDMM)), and (iv) the increase of alkyl groups produced self-reversible high contrast off-on fluorescence switching materials (TDEM). Powder X-ray diffraction studies indicate that stimuli induced reversible phase transformation from crystalline to amorphous and vice versa was responsible for fluorescence switching. The computational studies also supported that OCH3 substitution at ortho to acceptor increased the dihedral angle and optical band gap. Thus, the present studies provide a structural insight for designing TPA based organic molecules for developing new smart organic materials. Stimuli responsive smart fluorescent triphenylamine derivatives have been synthesized that exhibited reversible and self-reversible mechanochromism, and nonfluorescence solids depend on the position of substitution and acceptor structure. [ABSTRACT FROM AUTHOR]

The article provide information on the study concerning the construction of cyclic molecules in the U.S. The author infers that the construction of cyclic molecules has obtained much attention because of both scientific curiosity and their potential use in applications such as magnetic materials, sensors for small molecules, and new classes of catalysts.

Excited-state intramolecular proton transfer (ESIPT) compounds, 2-(2-((2-hydroxybenzylidine)amino)phenoxy)benzonitrile (1) and 2-(4-((2-hydroxy-4-methoxybenzylidine)amino)phenoxy)benzonitrile (2) exhibited aggregation induced enhanced emission (AIEE) in the solid state and nanofabrication mediated white light emission. The strong intermolecular interactions (H-bonding, C-H···π and π⋯π) restrict the free rotation and rigidify the fluorophores, 1 and 2, in the crystal lattice that lead to enhanced fluorescence in the solid state of 1 (yellow, λmax = 535 nm, Φf = 38%) and 2 (greenish-yellow, λmax = 525 nm, Φf = 21%). Surprisingly, nanofabrication of 1 and 2 produced metastable white light emitting nanoparticles (Φf = 24% (1), 19% (2)) that slowly converted into stable yellow (1) or greenish-yellow (2) fluorescent nanoparticles with increasing time. The time dependent fluorescence, morphological, and metal ion interacting studies indicate the formation of soft nanoparticles in which both blue fluorescent cyanophenoxy and yellow/greenish-yellow fluorescent salicylidene group behave independently. 1 and 2 nanoparticles undergo morphological change from spherical to plates with increasing time. Thus, simple ESIPT molecules showed solid-state fluorescent and nanofabrication induced tunable fluorescence, particularly white fluorescent metastable nanoparticles. [ABSTRACT FROM AUTHOR]

Flexible metal-organic frameworks (MOFs) show the structural transition phenomena, gate opening and breathing, upon the input of external stimuli. These phenomena have significant implications in their adsorptive applications. In this work, we demonstrate the direct capture of these gate-opening and breathing phenomena, triggered by CO2 molecules, in a well-designed flexible MOF composed of rotational sites and molecular gates. Combining X-ray single crystallographic data of a flexible MOF during gate opening/closing and breathing with in situ X-ray powder diffraction results uncovered the origin of this flexibility. Furthermore, computational studies revealed the specific sites required to open these gates by interaction with CO2 molecules. [ABSTRACT FROM AUTHOR]

Either an S8 symmetrical 48-membered hexadecanuclear or an S10 symmetrical 60-membered icosanuclear manganese metallamacrocycle was self-assembled using a manganese ion and a ditopic pentadentate ligand. This was either N-4-phenylbenzoylsalicylhydrazide (H3pbshz) containing a rigid rod-shaped, bulky biphenyl residue as a terminal N-acyl group or N-3,3-diphenylpropionylsalicylhydrazide (H3dppshz) containing a flexible β-branched N-acyl group, but with two sterically bulky phenyl residues at the Cβ position. The backbone of these metal-organic assemblies is a repeating unit consisting of a -[Mn-N-N-] link that extends to complete either the 48-membered cyclic structure involving 16 manganese(lll)centers and 16 ditopic linker ligands or the 60-membered cyclic structure involving 20 manganese(lll) centers and 20 ditopic linker ligands (depending on the ligand used). Even though the nuclearity of the metallamacrocycles was different, the successive manganese centers were in the same chiral sequence, ··· (ΛΛΛΛ)(ΛΛΛΛ)···. [ABSTRACT FROM AUTHOR]