Synthesis, X-ray Structure, Optical, and Electrochemical Properties of a White-Light-Emitting Molecule.

A new white-light-emitting molecule (1) was synthesized and characterized by NMR spectroscopy, high resolution mass spectrometry, and single-crystal X-ray diffraction. Compound 1 crystallizes in the orthorhombic space group Pnma, with a = 12.6814(6), b = 7.0824(4), c = 17.4628(9) Å, α = 90°, ß = 90°, γ = 90°. In the crystal, molecules are linked by weak intermolecular C-H···O hydrogen bonds, forming an infinite chain along [100], generating a C(10) motif. Compound 1 possesses an intramolecular six-membered-ring hydrogen bond, from which excited-state intramolecular proton transfer (ESIPT) takes place from the phenolic proton to the carbonyl oxygen, resulting in a tautomer that is in equilibrium with the normal species, exhibiting a dual emission that covers almost all of the visible spectrum and consequently generates white light. It exhibits one irreversible one-electron oxidation and two irreversible one-electron reductions in dichloromethane at modest potentials. Furthermore, the geometric structures, frontier molecular orbitals (MOs), and the potential energy curves (PECs) for 1 in the ground and the first singlet excited state were fully rationalized by density functional theory (DFT) and time-dependent DFT calculations. The results demonstrate that the forward and backward ESIPT may happen on a similar timescale, enabling the excited-state equilibrium to be established.

1,6- and 1,7-Regioisomers of Highly Soluble Amino-Substituted Perylene Tetracarboxylic Dianhydrides: Synthesis, Optical and Electrochemical Properties.

1,6- and 1,7-regioisomers of diamino-substituted perylene tetracarboxylic dianhydrides (PTCDs) with different n-alkyl chain lengths (n = 6, 12 or 18) were synthesized and characterized by NMR spectroscopy and high-resolution mass spectrometry. These dyes are highly soluble in most organic solvents and even in nonpolar solvents, such as hexane. To the best of our knowledge, this is the first time the 1,6-diamino-substituted PTCDs (2a-2c) have been obtained in pure form. The regioisomers 1a-1c (1,7-) and 2a-2c (1,6-) exhibit significant differences in their optical characteristics. In addition to the longest wavelength absorption band at around 674 nm, 2a-2c exhibit another shoulder band at ca. 600 nm, and consequently, cover a large part of the visible region relative to those of 1a-1c. Upon excitation, 2a-2c also show larger dipole moment changes than those of 1a-1c; the dipole moments of all compounds have been estimated using Lippert-Mataga equation. Moreover, all the dyes show a unique charge transfer emission in the near-infrared region, of which the peak wavelengths exhibit strong solvatochromism. They all exhibit one irreversible one-electron oxidation and two quasi-reversible one-electron reductions in dichloromethane at modest potentials. Complementary density functional theory calculations performed on these chromophores are reported in order to rationalize their electronic structure and optical properties.

Synthesis, X-ray structure, spectroscopic properties and DFT studies of a novel Schiff base.

A series of Schiff bases, salicylideneaniline derivatives 1-4, was synthesized under mild conditions and characterized by 1H NMR, HRMS, UV-Vis and fluorescence spectra, and single-crystal X-ray diffraction. In solid and aprotic solvents 1-4 exist mainly as E conformers that possess an intramolecular six-membered-ring hydrogen bond. A weak intramolecular C-H···F hydrogen bond is also observed in fluoro-functionalized Schiff base 4, which generates another S(6) ring motif. The C-H···F hydrogen bond further stabilizes its structure and leads it to form a planar configuration. Compounds 1-3 exhibit solely a long-wavelength proton-transfer tautomer emission, while dipole-functionalized Schiff base 4 shows remarkable dual emission originated from the excited-state intramolecular charge transfer (ESICT) and excited-state intramolecular proton transfer (ESIPT) states. Furthermore, the geometric structures, frontier molecular orbitals (MOs) and the potential energy curves for 1-4 in the ground and the first singlet excited state were fully rationalized by density functional theory (DFT) and time-dependent DFT calculations.

Ratiometric fluorescent/colorimetric cyanide-selective sensor based on excited-state intramolecular charge transfer-excited-state intramolecular proton transfer switching.

A novel salicylideneaniline-based fluorescent sensor, SB1, with a unique excited-state intramolecular charge transfer-excited-state intramolecular proton transfer (ESICT-ESIPT) coupled system was synthesized and demonstrated to fluorescently sense CN(-) with specific selectivity and high sensitivity in aqueous media based on ESICT-ESIPT switching. A large blue shift (96 nm) was also observed in the absorption spectra in response to CN(-). The bleaching of the color could be clearly observed by the naked eye. Moreover, SB1-based test strips were easily fabricated and low-cost, and could be used in practical and efficient CN(-) test kits. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations further support the cyanide-induced ESICT-ESIPT switching mechanism. The results provide the proof of concept that the colorimetric and ratiometric fluorescent cyanide-selective chemodosimeter can be created based on an ESICT-ESIPT coupled system.

Green Perylene Bisimide Dyes: Synthesis, Photophysical and Electrochemical Properties.

Three asymmetric amino-substituted perylene bisimide dyes with different n-alkyl chain lengths (n = 6, 12, or 18), 1-(N,N-dialkylamino)perylene bisimides (1a-1c), were synthesized under mild condition in high yields and were characterized by ¹H NMR, ¹³C NMR (nuclear magnetic resonance), HRMS (High Resolution Mass Spectrometer), UV-Vis and fluorescence spectra, as well as cyclic voltammetry (CV). These molecules show intense green color in both solution and solid state and are highly soluble in dichloromethane and even in nonpolar solvents, such as hexane. The shapes of the absorption spectra of 1a-1c in solid state and in solution were found to be virtually the same, indicating that the long alkyl chains could efficiently prevent aggregation. They exhibit a unique charge transfer emission in the near-infrared region, of which the peak wavelengths show strong solvatochromism. The dipole moments of the compounds have been estimated using the Lippert-Mataga equation, and upon excitation, they show larger dipole moment changes than that of 1-aminoperylene bisimide (2). Furthermore, all of the compounds exhibit two quasi-reversible one-electron oxidations and two quasi-reversible one-electron reductions in dichloromethane at modest potentials. Complementary density functional theory (DFT) calculations performed on these dyes are reported in order to rationalize their molecular structures and electronic properties.

1-Meth-oxy-11H-benzo[b]fluoren-11-one.

In the title compound, C18H12O2, the non-H atoms are nearly coplanar, the maximum atomic deviation being 0.113 (2) Å. π-π stacking is observed in the crystal structure, the shortest centroid-centroid distance being 3.5983 (19) Å. The mol-ecular packing is further stabilized by weak C-H⋯O hydrogen bonds, forming an infinite chain along [100] and generating a C(6) motif.

1,6- and 1,7-regioisomers of asymmetric and symmetric perylene bisimides: synthesis, characterization and optical properties.

The 1,6- and 1,7-regioisomers of dinitro- (1,6-A and 1,7-A) and diamino-substituted perylene bisimides (1,6-B and 1,7-B), and 1-amino-6-nitro- and 1-amino-7-nitroperylene bisimides (1,6-C and 1,7-C) were synthesized. The 1,6-A and 1,7-A regioisomers were successfully separated by high performance liquid chromatography and characterized by 500 MHz 1H-NMR spectroscopy, and subsequently, their reduction which afforded the corresponding diaminoperylene bisimides 1,6-B and 1,7-B, respectively. On the other hand, the monoreduction of 1,6-A and 1,7-A, giving the asymmetric 1-amino-6-nitro (1,6-C) and 1-amino-7-nitroperylene bisimides (1,7-C), respectively, can be performed by shortening the reaction time from 6 h to 1 h. This is the first time the asymmetric 1,6-disubstituted perylene bisimide 1,6-C is obtained in pure form. The photophysical properties of 1,6-A and 1,7-A were found to be almost the same. However, the regioisomers 1,6-C and 1,7-C, as well as 1,6-B and 1,7-B, exhibit significant differences in their optical characteristics. Time-dependent density functional theory calculations performed on these dyes are reported in order to rationalize their electronic structure and absorption spectra.

Penta-cyclo-[8.2.1.1(4,7).0(2,9).0(3,8)]tetra-deca-5,11-diene.

The title compound, C(14)H(16), was prepared through [2 + 2] cyclo-addition of norbornadiene. There are two independent mol-ecules in the asymmetric unit: each is centrosymmetric with the centroid of the four-membered ring located about an inversion center. Each mol-ecule possesses an exo-trans-exo conformation.

2-(4-Nitro-benzyl-idene)malononitrile.

In the title compound, C(10)H(5)N(3)O(2), the benzyl-idene-malono-nitrile unit is nearly planar, with a maximum deviation of 0.129 (2) Šfor a terminal N atom; the nitro group is approximately coplanar with the benzene ring [dihedral angle = 8.8 (3)°]. An intra-molecular C-H⋯N hydrogen bond stabilizes the mol-ecular conformation.

3-{[(4Z)-1,2-Dimethyl-5-oxoimidazol-4-yl-idene]meth-yl}-4-hy-droxy-benzonitrile.

In the title compound, C(13)H(11)N(3)O(2), an intra-molecular O-H⋯N hydrogen bond generates an S(7) ring. The dihedral angle between the mean plane of the benzene ring and the imidazolidinone ring is 3.05 (2)°. In the crystal, inversion-related mol-ecules are linked by dual C-H⋯O(carbon-yl) hydrogen bonds to form a dimer with an R(2) (2)(14) graph-set motif. A C-H⋯O(hy-droxy) inter-action links pairs of mol-ecules into another type of cyclic dimer with an R(2) (2)(18) motif. The mol-ecules are further linked by C-H⋯N inter-actions to form layers parallel to (001). Offset π-π stacking [3.3877 (8) Å] is observed in the crystal structure, with an inter-planar spacing between the planes of neighboring benzene rings of 3.444 (1) Å.

(Z)-4-(2-Hy-droxy-benzyl-idene)-1-methyl-2-phenyl-1H-imidazol-5(4H)-one.

In the title compound, C(17)H(14)N(2)O(2), the asymmetric unit comprises two mol-ecules that are comformationally similar [the dihedral angles between the phenyl rings in each are 46.35 (2) and 48.04 (3)°], with the conformation stabilized by intra-molecular O-H⋯N hydrogen bonds, which generate S(7) rings. In the crystal, inversion-related mol-ecules are linked by pairs of weak C-H⋯O hydrogen bonds, forming dimers with an R(2) (2)(16) graph-set motif. Weak inter-ring π-π stacking is observed in the structure, the shortest centroid-to-centroid distance being 3.7480 (13) Å.

(E)-4-[(4-Diethyl-amino-2-hy-droxy-benzyl-idene)amino]-benzonitrile.

The title compound, C(18)H(19)N(3)O, displays an E conformation with respect to the C=N double bond. The dihedral angle between the mean planes of the two benzene rings is 24.49 (3)°. An intra-molecular O-H⋯N hydrogen bond generates an S(6) ring. In the crystal, mol-ecules are linked by nonclassical inter-molecular C-H⋯O hydrogen bonds to form an infinite one-dimensional chain along [010], generating a C(8) motif.

3-Oxo-2,3-dihydro-1H-inden-4-yl acetate.

In the title compound, C(11)H(10)O(3), the 1-indanone unit is essentially planar (r.m.s. deviation = 0.036 Å). In the crystal, mol-ecules are linked by non-classical C-H⋯O hydrogen bonds, forming a C(6) chain along [010].

4-Hy-droxy-indan-1-one.

The mol-ecule of the title compound, C(9)H(8)O(2), is essentially planar except for the methyl-ene H atoms [maximum deviation = 0.028 (1) Å]. In the crystal, the mol-ecules are linked by classical O-H⋯O hydrogen bonds and weak C-H⋯O inter-actions into chains along [110] and [1-10].

rac-1,2,3,4-Tetra-hydro-1,4-methano-anthracene-6,7-dicarbonitrile.

The title compound, C(17)H(12)N(2), comprises a norbornane unit having a dicyanona-phthalene ring fused on one side. Both cyano groups are twisted slightly out of the plane of the naphthalene ring system [C-C-C-C torsion angle = 1.9 (2)°]. In the crystal, inversion-related mol-ecules are linked by pairs of weak C-H⋯N hydrogen bonds, forming dimers.

2-(2-Hy-droxy-phen-yl)-1,3-benzothia-zole-6-carbaldehyde.

The mol-ecule of the title compound, C(14)H(9)NO(2)S, is nearly planar, the maximum atomic deviation being 0.081 (2) Å. An intra-molecular O-H⋯N bond generates an S(6) ring motif. In the crystal, inversion-related mol-ecules linked by a pair of weak C-H⋯O hydrogen bonds form a supra-molecular dimer. π-π stacking is observed between the thia-zole and benzene rings of adjacent mol-ecules, the centroid-centroid distance being 3.7679 (9) Å.