Mesoporous Carbon/α-Fe2O3 Nanoleaf Composites for Disposable Nitrite Sensors and Energy Storage Applications.

In this work, we report a novel hydrothermal synthesis of α-Fe2O3 nanoleaf-incorporated mesoporous carbon-chitosan (α-Fe2O3@MPC-chit) as a versatile disposable sensor for selective electrochemical detection of nitrite and for supercapacitor applications. The newly synthesized α-Fe2O3@MPC-chit nanocomposite was characterized by scanning electron microscopy, X-ray diffraction, Fourier transform-infrared spectroscopy, UV, and Raman spectroscopy. The extensive physicochemical characterization reveals the strong immobilization of α-Fe2O3 nanoleaves within the MPC-chit composite. The electrochemical characterization with cyclic voltammetry and impedance spectroscopy using [Fe(CN)6)]3-/4- as a redox probe concludes good electron conductivity and efficient electron transfer behavior of α-Fe2O3@MPC-chit. The α-Fe2O3@MPC-chit modified electrode exhibits excellent electrocatalytic activity toward nitrite oxidation. The amperometric method of nitrite detection showed a linear range of up to 200 µmol L-1 . The current sensitivity and detection limit were found to be 0.913 µA µM-1 and 31 nM cm-2, respectively. The improved catalytic activity of the proposed electrode was endorsed by the synergistic effect of α-Fe2O3 with the MPC-chit composite. The ability of the proposed electrode was demonstrated by the successful detection of nitrite present in tap water, river water, and industrial samples with extensive recovery values. Furthermore, the α-Fe2O3@MPC-chit modified stainless-steel electrode showed high-performance supercapacitor application and exhibited a large specific capacitance of 380 F g-1 at 1 A g-1.

Unusual Behavior of Donor-Acceptor Stenhouse Adducts in Confined Space of a Water-Soluble PdII8 Molecular Vessel.

Donor-acceptor Stenhouse adducts (DASA) are new-generation photochromic compounds discovered recently. DASA exist normally in open form (blue/violet) and readily convert to cyclic (light yellow/colorless) zwitterionic form reversibly in the presence of green light in toluene/dioxane. In aqueous medium, the open form is not stable and converts to the cyclic zwitterionic form irreversibly. We report here a new self-assembled Pd8 molecular vessel (MV) that can stabilize and store the open form of DASA even in aqueous medium. Reaction of the 90° acceptor cis-(tmeda)Pd(NO3)2 (M) [tmeda = N, N, N', N'-tetramethylethane-1,2-diamine] with a symmetric tetraimidazole donor (L, 3,3',5,5'-tetra(1 H-imidazol-1-yl)-1,1'-biphenyl) in a 2:1 molar ratio yielded a water-soluble [8+4] self-assembled M8L4 molecular barrel (MV). This barrel (MV) is found to be a potential molecular vessel to store and stabilize the open forms of DASA in aqueous medium over the more stable zwitterionic cyclic form, while in the absence of the barrel the same DASA exist in cyclic zwitterionic form in aqueous medium. The hydrophobic interaction between the cavity and the open form of DASA molecules benefits reaching an out-of-equilibrium or reverse equilibrium state in aqueous medium. The presence of excess MV could even drive the conversion of the stable cyclic form to the open form in aqueous medium. The host-guest complex is stable upon irradiating with green light. To the best of our knowledge, this is the first successful attempt to stabilize the open form of DASA molecules in aqueous medium and the first report on the fate of DASA in a confined space discrete molecular architecture. Furthermore, the molecular vessel has been utilized for catalytic Michael addition reactions of a series of nitrostyrene derivatives with 1,3-indandione in aqueous medium.

A novel multicomponent quadruple/double quadruple domino reaction: highly efficient synthesis of polyheterocyclic architectures.

A novel multicomponent quadruple domino reaction (MCQDR) for the assembly of structurally complex molecular architectures via the formation of three rings and three contiguous stereogenic centers has been accomplished with high regio- and diastereoselectivity. Solvents, catalysts and work-up were not required to obtain the target molecules. In addition, this new protocol is also extended for the multicomponent double quadruple domino reaction (MCDQDR) to create novel polyheterocyclic architectures in an orthogonal manner.

A Discrete Self-Assembled Pd12 Triangular Orthobicupola Cage and its Use for Intramolecular Cycloaddition.

Water-soluble Pd12 L6 coordination cage TC-1 was synthesized by coordination-driven self-assembly of symmetrical tetrapyridyl donor L with 90° ditopic acceptor cis-[Pd(NO3 )2 (tmeda)] [tmeda=N,N,N',N'-tetramethylethane-1,2-diamine]. The Pd12 L6 coordination assembly is an uncommon example of a coordination cage having triangular orthobicupola-like geometry. It was characterized by multinuclear NMR spectroscopy, ESI-MS, and single-crystal X-ray diffraction. Self-assembly of a tetratopic donor with a cis-blocked 90° ditopic acceptor generally yields tri-/tetra-/hexagonal barrels or closed cubic cages. However, in the present case the donor and acceptor are arranged in an unusual fashion to generate an orthobicupola geometry in which two triangular cupola share a common irregular hexagonal face. The cage was used to perform intramolecular cycloaddition reactions of O-propargylated benzylidinebarbituric acid derivatives in nitromethane. Several penta-/tetracyclouracil derivatives were synthesized through cage-catalyzed [4+2] cycloaddition reactions in a concerted manner with good to high conversion under mild reaction conditions, whereas in the absence of cage TC-1 similar reactions led to lower conversion to the cyclized products in organic solvent. This approach is of particular importance compared to the literature reports on the synthesis of similar compounds under high-temperature reflux conditions with high catalyst loading.

Preparation of a chiral Pt12 tetrahedral cage and its use in catalytic Michael addition reaction.

The reaction of chiral cis-[(1S,2S)-dch]Pt(NO3)2 (M) [where (1S,2S)-dch = (1S,2S)-1,2-diaminocyclohexane] with a hexadentate ligand (L) in 3 : 1 stoichiometric ratio yielded a [12+4] self-assembled chiral M12L4 molecular tetrahedron (T). The cage T features an internal 3D nanocavity with large open 'windows', enabling it to catalyze Michael addition reactions of a series of nitrostyrene derivatives with indole in a 9 : 1 water : methanol mixture.

Catalytic Intramolecular Cycloaddition Reactions by Using a Discrete Molecular Architecture.

A discrete tetragonal tube-shaped complex (MT-1) has been synthesised by coordination-driven self-assembly of a carbazole-based tetraimidazole donor L and a Pd(II) 90° acceptor, that is, [cis-(dppf)Pd(OTf)2 ] (dppf=diphenylphosphinoferrocene, OTf=CF3 SO3- ). Complex MT-1 was characterised by multinuclear NMR, ESI-MS and single-crystal X-ray diffraction analysis (SCXRD), which showed its symmetrical tetrafacial tube-shaped architecture possessing a large cavity described by four aromatic walls. This coordination cage was successfully utilised as a molecular vessel to perform intramolecular cycloaddition reactions of O-allylated benzylidinebarbituric acid derivatives inside its confined nanospace. The presence of a catalytic amount of MT-1 promoted [4+2] cycloaddition reactions in a regio- and stereoselective manner, yielding the corresponding penta/tetracyclouracil derivatives in good yields under mild reaction conditions. This protocol is interesting compared with the literature reports for the synthesis of similar chromenopyran pyrimidinedione derivatives under high-temperature reflux conditions or solid-state melt reactions (SSMRs).

Methyl 3'-benzyl-4'-(2,4-di-chloro-phen-yl)-1'-methyl-2-oxo-1-propyl-spiro-[indoline-3,2'-pyrrolidine]-3'-carboxy-l-ate.

In the title compound, C30H30Cl2N2O3, the indole ring system is roughly planar, with a maximum deviation of 0.1039 (18) Šfor the carbonyl C atom, and makes a dihedral angle of 86.61 (9)° with the mean plane of the pyrrolidine ring. This spiro pyrrolidine ring adopts an envelope conformation with the N atom at the flap position. The pyrrole ring of the indole ring system adopts a twisted conformation on the C-C(=O) bond. The mol-ecular structure is stabilized by an intra-molecular C-H⋯O hydrogen bond, which generates an S(6) ring motif, and a π-π inter-action [centroid-centroid distance = 3.6577 (12) Å] involving the 2,4-di-chloro-phenyl ring and the benzyl ring. In the crystal, mol-ecules are linked via C-H⋯O hydrogen bonds, forming C(9) chains running parallel to [10-1].

Methyl 4'-(3-bromo-phen-yl)-3'-(2,5-di-methyl-benz-yl)-1'-methyl-2-oxo-spiro-[indo-line-3,2'-pyrrolidine]-3'-carboxyl-ate.

In the title compound, C29H29BrN2O3, the indole ring system is essentially planar (r.m.s. deviation = 0.079 Å) and makes a dihedral angle of 85.23 (10)° with the mean plane of the 4-methyl-pyrrolidine ring. This ring adopts an envelope conformation with the N atom at the flap. The pyrrolidine ring of the indole ring system adopts a twisted conformation on the C-C(=O) bond. The mol-ecular structure is stabilized by an intra-molecular C-H⋯O hydrogen bond, which generates an S(6) ring motif. In the crystal, mol-ecules are linked via pairs of C-H⋯O hydrogen bonds, forming inversion dimers with an R 2 (2)(14) ring motif. These dimers are further linked by N-H⋯O and C-H⋯O hydrogen bonds, forming two-dimensional networks lying parallel to (10-1).

Methyl 3'-benzyl-4'-(2,4-di-chloro-phen-yl)-1'-methyl-2-oxo-spiro-[indoline-3,2'-pyrrolidine]-3'-carboxyl-ate.

In the title compound, C27H24Cl2N2O3, the indole ring system is essentially planar, with a maximum deviation of 0.082 (2) Šfor the carbonyl C atom. It makes a dihedral angle of 88.53 (6)° with the mean plane of the 4-methyl-pyrrolidine ring, which adopts an envelope conformation with the N atom at the flap position. The mol-ecular structure is stabilized by intra-molecular C-H⋯O hydrogen bonds, which generate S(6) and S(7) ring motifs, and an intra-molecular π-π inter-action involving the benzyl and di-chloro-substituted benzene rings [centroid-centroid distance = 3.6291 (11) Å]. In the crystal, mol-ecules are linked via N-H⋯O hydrogen bonds, forming C(7) chains running parallel to [10-1].

Methyl 3'-(2,5-di-methyl-benz-yl)-1'-methyl-2-oxo-4'-phenyl-spiro-[indoline-3,2'-pyrrolidine]-3'-carboxyl-ate chloro-form monosolvate.

In the title solvate, C29H30N2O3·CHCl3, the dihedral angle between the indole ring system (r.m.s. deviation = 0.050 Å) and the 4-methyl-pyrrolidine ring is 88.88 (8)°. The latter ring adopts an envelope conformation with the N atom as the flap. Its mean plane makes dihedral angles of 86.94 (11) and 42.08 (9)° with the phenyl and di-methyl-benzene rings, respectively. The mol-ecular conformation is stabilized by intra-molecular C-H⋯O hydrogen bonds, which generate S(6) and S(9) ring motifs. The chloro-form solvent mol-ecule is linked to the organic mol-ecule by a C-H⋯O hydrogen bond involving the carbonyl O atom of the carboxyl-ate group. In the crystal, mol-ecules are linked via bifurcated N-H⋯(N,O) and C-H⋯O hydrogen bonds, forming chains propagating along [001].

Methyl (2Z)-2-bromo-methyl-3-(2,4-dichloro-phen-yl)prop-2-enoate.

In the title compound C11H9BrCl2O2, which represents the Z isomer, the methyl-acrylate moiety is essentially planar within 0.039 (2) Šand has an extended trans configuration. The benzene ring makes a dihedral angle of 28.3 (1)° with the mean plane of the methyl-acrylate moiety. The crystal packing is characterized by C-H⋯O hydrogen bonding and halogen-halogen inter-actions [Cl⋯Cl = 3.486 (3) Å], resulting in the formation of R 2 (2)(11) ring motifs and connecting the mol-ecules into chains propagating along the b axis.

(E)-Methyl 2-benzyl-3-o-tolyl-acrylate.

In the title compound, C(18)H(18)O(2), the methyl acrylate substituent adopts an extended E conformation with all torsion angles close to 180°. The mean plane of the acrylate unit and the phenyl ring are approximately orthogonal to each other, making a dihedral angle of 81.40 (6)°. The position of the carbonyl group with respect to the olefinic double bond is typically S-trans. The crystal packing is stabilized by inter-molecular C-H⋯π inter-actions.

2-[(6-Nitro-1,3-benzodioxol-5-yl)methyl-idene]malononitrile.

In the title compound, C(11)H(5)N(3)O(4), the nitro group is rotated by 29.91 (16)° out of the plane of the adjacent aryl ring. The 1,3-benzodioxole ring is nearly planar, with a maximium deviation of 0.0562 (10) Å. The dioxolene ring adopts an envelope conformation on the O-C-O C atom. In the crystal, mol-ecules are linked via C-H⋯O inter-actions, resulting in R(2) (2)(6) and R(2) (2)(12) graph-set motifs.