Synthesis of Small Fluorescent Molecules and Evaluation of Photophysical Properties.

A series of aniline-based fluorophores were newly synthesized. To increase their fluorescence quantum yields, it was particularly important to substitute 3,3,3-trifluoroprop-1-enyl (TFPE) groups next to the amino group to benefit from an extended π-electron delocalization. Among these, 5-CN-2-TFPE-aniline was found to behave as an excellent fluorophore with a reasonable fluorescence quantum yield of 0.89 even in aqueous solution. l-Alanine peptide, a nonfluorescent analogue of 5-CN-2-TFPE-aniline, was synthesized and successfully employed as an enzyme probe to detect aminopeptidase N activity.

Combined Experimental and Theoretical Studies on Planar Chirality of Partially Overlapped C2-Symmetric [3.3](3,9)Dicarbazolophanes.

Partially overlapped dicarbazolophanes exhibit a planar chirality. In this study, C2-symmetrical [3.3](3,9)dicarbazolophane derivatives (CZ1-CZ3) have been optically resolved by preparative chiral high-performance liquid chromatography for the first time. In their circular dichroism (CD) spectra, moderate Cotton effects (CEs) were observed for their 1Lb and 1La transitions (|Δε| = 10-12 and 51-57 M-1 cm-1, respectively), while intense CEs were notified in their 1B transitions (|Δε| = 156-216 M-1 cm-1), absorption dissymmetry (gabs) factors being in orders of 10-2. Circularly polarized luminescence spectrum was also obtained for cyanamide derivative CZ1, with a comparative luminescence dissymmetry (glum) factor of 0.013. A computational investigation was applied to address the factors for such remarkable chiroptical responses in these dicarbazolophanes of planar chirality. Absolute configurations were unambiguously determined by the comparison of experimental and theoretical CD spectra, which was affirmed by the X-ray crystal structural analysis of enantiomerically pure sulfonamide derivative CZ2.

Development of a fluorogenic small substrate for dipeptidyl peptidase-4.

A series of aniline and m-phenylenediamine derivatives with electron-withdrawing 3,3,3-trifluoropropenyl substituents were synthesized as small and chemically stable fluorescent organic compounds. Their fluorescence performances were evaluated by converting 2,4-disubstituted aniline 1 to the non-fluorescent dipeptide analogue H-Gly-Pro-1 for the use as a fluorogenic substrate for dipeptidyl peptidase-4 (DPP-4). The progress of the enzymatic hydrolysis of H-Gly-Pro-1 with DPP-4 was monitored by fluorometric determination of 1 released into the reaction medium. The results suggest that 1 could be used as fluorophore in OFF-ON-type fluorogenic probes.

Dynamical excimer formation in rigid carbazolophane via charge transfer state.

Formation dynamics of intramolecular excimer in dioxa[3.3](3,6)carbazolophane (CzOCz) was studied by time-resolved spectroscopic methods and computational calculations. In the ground state, the most stable conformer in CzOCz is the anti-conformation where two carbazole rings are in antiparallel alignment. No other isomers were observed even after the solution was heated up to 150 °C, although three characteristic isomers were found by the molecular mechanics calculation: the first is the anti-conformer, the second is the syn-conformer where two carbazole rings are stacked in the same direction, and the third is the int-conformer where two carbazole rings are aligned in an edge-to-face geometry. Because of the anti-conformation, the interchromophoric interaction in CzOCz is negligible in the ground state. Nonetheless, the intramolecular excimer in CzOCz was dynamically formed in an acetonitrile (MeCN) solution, indicating strong interchromophoric interaction and the isomerization from the anti- to syn-conformation in the excited state. The excimer formation in CzOCz is more efficient in polar solvents than in less polar solvents, suggesting the contribution of the charge transfer (CT) state to the excimer formation. The stabilization in the excited state is discussed in terms of molecular orbital interaction between two carbazole rings. The solvent-polarity-induced excimer formation is discussed in terms of the CT character in the int-conformation.

Di-µ 2-acetato-1:2κ (2) O:O';2:3κ (2) O:O'-bis-{µ 2-4,4'-di-chloro-2,2'-[2,2-di-methyl-propane-1,3-diylbis(nitrilo-methanylyl-idene)]diphenolato}-1:2κ (6) O,N,N',O':O,O';2:3κ (6) O,O':O,N,N',O'-tri-cadmium.

In the title linear homo-trinuclear complex, [Cd3(C19H18Cl2N2O2)2(C2H3O2)2], the central Cd(II) atom is located on a centre of inversion and has a distorted octa-hedral coordination geometry formed by four O atoms from two bidentate/tetra-dentate Schiff base ligands and two O atoms from two bridging acetate ligands. The coordination geometry of the terminal Cd(II) atom is square-pyramidal with the tetra-dentate part of the ligand in the basal plane and one O atom from an acetate ligand occupying the apical site. The six-membered CdN2C3 ring adopts a chair conformation. The acetate-bridged Cd⋯Cd distance is 3.3071 (2) Å. The crystal structure is stabilized by C-H⋯O hydrogen bonds, which form C(7) chain motifs and give rise to a two-dimensional supra-molecular network structure lying parallel to the ab plane.

Crystal structure of poly[(aceto-nitrile-κN)(µ3-7-{[bis-(pyridin-2-ylmeth-yl)amino]-meth-yl}-8-hy-droxy-quinoline-5-sulfonato-κ4N,O:O':O'')sodium].

In the title compound, [Na(C22H19N4O4S)(CH3CN)]n, the NaI atom adopts a distorted square-pyramidal coordination geometry, formed by one N and one O atom of the qunolinol moiety in the ligand, two O atoms of sulfonate moieties of two adjacent ligands and the N atom of the coordinated aceto-nitrile solvent. The NaI atom is located well above the mean basal plane of the square-based pyramid. The apical position is occupied by a sulfonate O atom of a neighboring ligand. Three N atoms of the bis-(pyridin-2-ylmeth-yl)amine moiety in the ligand are not coordinated by the sodium atom. The mol-ecule forms an intra-molecular bifurcated O-H⋯[N(tertiary amine),N(pyridine)] hydrogen bond, generating S(6) and S(5) rings. In the crystal, four mol-ecules are linked by four Na-O(sulfonato) bridged coordination bonds, forming a supra-molecular centrosymmetric tetra-mer unit comprising an eight-membered ring, and generating a two-dimensional network sheet. The mol-ecules of different sheets form inter-molecular C-H⋯O hydrogen bonds, and thereby a three-dimensional network structure.

Di-µ(2)-acetato-1:2κ(2)O:O';2:3κ(2)O:O'-bis-{µ(2)-4,4'-dichloro-2,2'-[2,2-dimethyl-propane-1,3-diylbis(nitrilo-methanylyl-idene)]diphenolato}-1:2κ(6)O,N,N',O':O,O';2:3κ(6)O,O':O,N,N',O'-tricopper(II).

The title compound, [Cu(3)(C(19)H(18)Cl(2)N(2)O(2))(2)(CH(3)CO(2))(2)], is a linear homo-trinuclear Cu(II) complex. The central Cu(II) atom is located on a centre of inversion and has a distorted octa-hedral coordination environment formed by six O atoms from two tetra-dentate Schiff base ligands and two bridging acetate ligands. The coordination geometry of the terminal Cu(II) atom is square-pyramidal with a tetra-dentate ligand in the basal plane. The apical site is occupied by one O atom from an acetate ligand. The acetate-bridged Cu⋯Cu distance is 3.0910 (5) Å. An intra-molecular C-H⋯O hydrogen bond forms an S(6) ring motif. The crystal of the trinuclear complex is stabilized by C-H⋯O hydrogen bonds.

Crystal structure of (7-{[bis-(pyridin-2-ylmeth-yl)amino-κ3 N,N',N'']meth-yl}-5-chloro-quinolin-8-ol)di-bromidozinc(II).

In the title compound, [ZnBr2(C22H19ClN4O)], the ZnII atom adopts a distorted square-pyramidal coordination geometry, formed by two bromido ligands and three N atoms of the bis-(pyridin-2-ylmeth-yl)amine moiety in the penta-dentate ligand containing quinolinol. The ZnII atom is located well above the mean basal plane of the square-based pyramid. The apical position is occupied by a Br atom. The O and N atoms of the quinolinol moiety in the ligand are not coordinated to the ZnII atom. An intra-molecular O-H⋯N hydrogen bond, generating an S(5) ring motif, stabilizes the mol-ecular structure. In the crystal, the mol-ecules are linked by inter-molecular C-H⋯Br hydrogen bonds, generating ribbon structures containing alternating R 2 2(22) and R 2 2(14) rings. These ribbons are linked through an inter-molecular C-H⋯Br hydrogen bond, forming a two-dimensional network sheet.

Synthesis and crystal structure of anti-10-butyl-10,11,22,23-tetra-hydro-9H,21H-5,8:15,12-bis(metheno)[1,5,11]tri-aza-cyclo-hexa-decino[1,16-a:5,6-a']di-indole.

The title compound, C33H33N3, is a carbazolophane, which is a cyclo-phane composed of two carbazole fragments. It has a planar chirality but crystallizes as a racemate in the space group P . The mol-ecule adopts an anti-configuration, in which two carbazole fragments are partially overlapped. Both carbazole ring systems are slightly bent, with the C atoms at 3-positions showing the largest deviations from the mean planes. The dihedral angle between two carbazole fragments is 5.19 (3)°, allowing an intra-molecular slipped π-π inter-action [Cg⋯Cg = 3.2514 (8) Å]. In the crystal, the mol-ecules are linked via inter-molecular C-H⋯N hydrogen bonds and C-H⋯π inter-actions into a network sheet parallel to the ab plane. The mol-ecules of different sheets form other C-H⋯π inter-actions, thus forming a three-dimensional network.

1,2-Bis[5-(9-ethyl-9H-carbazol-3-yl)-2-methyl-thio-phen-3-yl]-3,3,4,4,5,5-hexa-fluoro-cyclo-pentene.

The title compound, C(43)H(32)F(6)N(2)S(2), is a new symmetrical photochromic diaryl-ethene derivative with 9-ethyl-carbazol-3-yl substituents. The mol-ecule adopts a photoactive anti-parallel conformation [Irie (2000). Chem. Rev.100, 1685-1716; Kobatake et al. (2002). Chem. Commun. pp. 2804-2805], with a dihedral angle between the mean planes of the two thio-phene rings of 56.23 (6)°. The distance between the two reactive C atoms is 3.497 (3) Å. In the crystal, two mol-ecules are associated through a pair of C-H⋯F inter-molecular hydrogen bonds, forming a centrosymmetric dimer. Dimers are linked by weak π-π inter-actions [centroid-centroid distance = 3.8872 (13) Å], forming chains along the c axis.

Efficient carrier separation from a photochromic diarylethene layer.

Electrical carrier separation from a photoexcited photochromic molecule could be a promising method for controlling the photosensitivity of such a molecule. We report an efficient carrier separation from a photochromic diarylethene (DAE) molecule by adopting a device structure with a heterojunction consisting of an n-type diarylethene layer and a p-type layer of N,N'-di(1-naphthyl)-N,N'-diphenylbenzidine (NPB). A photocurrent originating from carrier separation for the colored photostationary state was observed, even at zero applied voltage. The efficient carrier separation occurred at the interface between the DAE and NPB layers and was the result of the internal electrical field induced by the pn heterojunction.

Aqua-{4,4',6,6'-tetra-fluoro-2,2'-[(piperazine-1,4-di-yl)dimethyl-ene]diphenolato}copper(II).

In the title compound, [Cu(C(18)H(16)F(4)N(2)O(2))(H(2)O)], the Cu(II) atom shows a distorted square-pyramidal coordination geometry with the N,N',O,O'-tetra-dentate piperazine-diphenolate ligand forming the basal plane. The apical site is occupied by the O atom of a coordinated water mol-ecule. Neighbouring complexes are associated through inter-molecular O-H⋯O and O-H⋯F hydrogen bonds between the water mol-ecule and a phenolate O atom or an F atom from an adjacent ligand, respectively, forming a centrosymmetric dimer. Dimers are linked by additional inter-molecular C-H⋯O and C-H⋯F hydrogen bonds, giving infinite chains propagating along the a axis.

Bis[µ-4,4',6,6'-tetra-chloro-2,2'-(piperazine-1,4-diyldimethyl-ene)diphenolato]dicopper(II).

In the centrosymmetric dinuclear Cu(II) title complex, [Cu(2)(C(18)H(16)Cl(4)N(2)O(2))(2)], the Cu(II) atom adopts a square-pyramidal geometry with a tetra-dentate ligand in the basal plane. The apical site is occupied by a phenolate O atom from an adjacent ligand, forming a dimer. The mol-ecular structure is stabilized by intra-molecular C-H⋯O and C-H⋯Cl hydrogen bonds.

4,4'-Dichloro-2,2'-(piperazine-1,4-diyldimethyl-ene)diphenol.

In the titile compound, C(18)H(20)Cl(2)N(2)O(2), the piperazine ring adopts a chair conformation. The mol-ecule has a non-crystallographic inversion centre in the middle of the piperazine ring at approximate position (3/4, 1/8, 3/8). There are intra-molecular O-H⋯N hydrogen bonds forming S(6) ring motifs. Inter-molecular C-H⋯O hydrogen bonds generate anti-parallel C(5) chain motifs propagating along the b axis, forming sheets parallel to the bc plane with a first-level graph-set S(6)C(5)R(6) (6)(26).

A monoclinic polymorph of 4,4'-dichloro-2,2'-(piperazine-1,4-diyl-dimethyl-ene)diphenol.

The titile compound, C(18)H(20)Cl(2)N(2)O(2), crystallizes as a monoclinic form in the space group P2(1)/n, with Z' = 1/2. It is polymorphic with the previously reported orthorhombic form [Kubono, Tsuno, Tani & Yokoi (2008). Acta Cryst. E64, o2309]. In the present polymorph, the mol-ecule lies on a crystallographic inversion centre at the piperazine ring centroid. An intra-molecular O-H⋯N hydrogen bond forms an S(6) ring motif. Inter-molecular C-H⋯O hydrogen bonding generates a C(5) chain motif propagating along the b axis, forming sheets parallel to (02) with a first-level graph set S(6)C(5)R(6) (6)(34).

Crystal Structure of (E)-2-(3,3,3-tri-fluoro-prop-1-en-1-yl)aniline.

The mol-ecule of the title compound, C9H8F3N, adopts an E configuration with respect to the C=C double bond. The dihedral angle between the benzene ring and the prop-1-enyl group is 25.4 (3)°. In the crystal, mol-ecules are linked via pairs of N-H⋯F hydrogen bonds into inversion dimers with an R 2 2(16) ring motif. The dimers are linked by C-H⋯N hydrogen bonds, forming a ribbon structure along the b-axis direction. The ribbons are linked by N-H⋯π and C-H⋯π inter-actions, generating a three-dimensional network.

Intramolecular singlet and triplet excimers of triply bridged [3.3.N](3,6,9)carbazolophanes.

Intermoiety electronic interactions in the singlet and triplet excimer states of triply bridged [3.3.n](3,6,9)carbazolophanes ([3.3.n]Cz, n=3-6) were studied by emission and transient absorption measurements. In these [3.3.n]Cz molecules, the dihedral angle and the separation distance r between fully overlapped two carbazole rings change systematically from nearly parallel (n=3, r=3.35 A) to oblique (n=6, r=4.03 A). In rigid glass at 77 K, [3.3.n]Cz (n=3, 4) (r<4 A) exhibited red-shifted and structureless excimer fluorescence and phosphorescence while [3.3.n]Cz (n=5, 6) (r>4 A) exhibited monomer-like vibrational fluorescence and phosphorescence. In solution at 130 K, all [3.3.n]Cz molecules exhibited an excimeric fluorescence band while [3.3.5]Cz still exhibited monomer-like phosphorescence. Transient absorption spectra measured at 294 K exhibited local excitation and charge-transfer bands for all [3.3.n]Cz molecules in the excited singlet and triplet states, suggesting that not only singlet but also triplet excimers of carbazole are formed at room temperature. Furthermore, the singlet-triplet energy gap decreased with the decrease in n, suggesting that electrons are effectively delocalized over the two carbazole moieties. These findings showed that both singlet and triplet excimers of carbazole are formed with a separation distance shorter than about 4 A and are most stable in the parallel-sandwich structure and that the configurational mixing between exciton resonance and charge resonance states plays an essential role in the formation of singlet and triplet excimers of carbazole.

Crystal structure of 7-hy-droxy-8-[(4-methyl-piperazin-1-yl)meth-yl]-2H-chromen-2-one.

In the title compound, C15H18N2O3, the coumarin ring is essentially planar, with an r.m.s. deviation of 0.012 Å. An intra-molecular O-H⋯N hydrogen bond forms an S(6) ring motif. The piperazine ring adopts a chair conformation. In the crystal, a C-H⋯O hydrogen bond generates a C(4) chain motif running along the c axis. The chain structure is stabilized by a C-H⋯π inter-action. The chains are linked by π-π inter-actions [centroid-centroid distance of 3.5745 (11) Å], forming a sheet structure parallel to the bc plane.

Intramolecular excimer emission of triply bridged [3.3.N](3,6,9)carbazolophanes.

The photophysical properties of a series of triply bridged [3.3.n](3,6,9)carbazolophanes ([3.3.n]Cz, n = 3, 4, 5, 6) were studied as a model compound for a fully overlapped carbazole excimer. In these [3.3.n]Cz molecules, a plane angle of the two carbazole moieties changed systematically from nearly parallel to oblique, with increases in the length of the methylene chain n bridging at the 9-position of each carbazole ring. Absorption bands of [3.3.n]Cz showed the blue-shift and the splitting for (1)L(a) <-- (1)A and (1)L(b) <-- (1)A transition bands of the reference carbazole monomer, respectively. These spectral changes in [3.3.n]Cz were explained by Kasha's molecular exciton theory with the distance r and dihedral angle theta between the carbazole moieties in the ground state. In both liquid and glass matrixes, [3.3.n]Cz showed intramolecular excimer emission. The emission peak wavelength changed from 409 nm (n = 6) to 480 nm (n = 3) depending on r in the ground state. The dependence of the peak wavelength on r clearly showed that relative configurations of carbazole moieties in the ground state were preserved even in the excimer states. The smaller radiative rate of the excimer emission than the reference monomer was explained by the dimer symmetry of [3.3.n]Cz.

Crystal structure of 7-{[bis-(pyridin-2-ylmeth-yl)amino]-meth-yl}-5-chloro-quinolin-8-ol.

In the title compound, C22H19ClN4O, the quinolinol moiety is almost planar [r.m.s. deviation = 0.012 Å]. There is an intra-molecular O-H⋯N hydrogen bond involving the hy-droxy group and a pyridine N atom forming an S(9) ring motif. The dihedral angles between the planes of the quinolinol moiety and the pyridine rings are 44.15 (9) and 36.85 (9)°. In the crystal, mol-ecules are linked via C-H⋯O hydrogen bonds forming inversion dimers with an R 4 (4)(10) ring motif. The dimers are linked by C-H⋯N hydrogen bonds, forming ribbons along [01-1]. The ribbons are linked by C-H⋯π and π-π inter-actions [inter-centroid distance = 3.7109 (11) Å], forming layers parallel to (01-1).