4-quinolin-8-yloxy Linked Triphenylamine Based Polyimides: Blue Light Emissive and Potential Hole-Transport Materials.

A series of fluorescent donor- acceptor (D-A) alternating copolyimides (P1, P2, P3 and P4) with 4-quinolin-8-yloxy linked triphenylamine main polymer chain have been synthesized by conventional polycondensation. All the synthesized co-polyimides were characterized by elemental, gel permeation chromatography and FTIR spectral analysis. These newly prepared PIs possess HOMO energy levels in range of - 4.74 to - 4.78 eV and have medium optical band gaps. The photoluminescence spectral analysis revealed blue to violet emission with appreciable efficiency with lower onset oxidation potentials suitable for the facile hole injection materials. All the photophysical and electrochemical properties were also explored in context of effect of the pendant 4- quinolin-8-yloxy, indicating suitable combination of donor (TPA) on one hand and imide and pendant as acceptor on both ends.Graphical Abstract.

A comparative study of the influence of N,N'-dialkyl vs. N,N'-diaryl-based electron donor ancillary ligands on photocurrent and photovoltage in dye-sensitized solar cells (DSSCs).

In this study, we report the synthesis of a novel heteroleptic Ru(ii)-sensitizer, (Ru(2,2'-bipyridine-4,4'-dicarboxylic acid)-4,4'-bis(4-piperidin-1-yl)phenyl ethenyl)-(2,2'-bipyridine) (NCS)2, denoted as SD-1; moreover, its photophysical, electrochemical, and photovoltaic performances were compared with those of N719 and K77-7 (N,N'-diaryl Ru-sensitizer, namely Ru(2,2'-bipyridine-4,4'-dicarboxylic-acid)-4,4'-bis(2-(4-N,N'-diphenylaminophenyl)ethenyl)-2,2'-bipyridine (NCS)2). The photovoltaic performance of SD-1 outperformed those of N-719 and K77-7, particularly in the red region, and the overall efficiency of SD-1 was 8.5% as compared to 8.0% of K77-7 and 7.7% of N719 under the same experimental device conditions. The superior light harvesting efficiency of SD-1 can be attributed to the strong electron donor sp3-nitrogen, which is attached to two sp3-carbons (dialkyl), whereas in the case of K77-7, all carbon atoms attached to the sp3-nitrogen are sp2, which decrease the electron density on the latter and minimize the electron-donating power of the ancillary ligand in K77-7. To gain a quantitative understanding of the electron density on nitrogen in SD-1 and K77-7, first-principle calculations using molecular and thermodynamic descriptors, such as frontier molecular orbitals, ground-state oxidation potential (GSOP), excited-state oxidation potential (ESOP), optical gap (E0-0), and charge distributions, were conducted in solution. In addition, for understanding the anchored structures of dyes on Ti24O48, density functional theory (DFT) and time-dependent density functional theory (TD-DFT) were utilized. Results of computational studies are in excellent agreement with the experimental results, which can be used as a screening tool for the design of more efficient molecular motifs for DSSCs.

Preparation, characterization, and enhanced thermal and mechanical properties of epoxy-titania composites.

This paper presents the synthesis and thermal and mechanical properties of epoxy-titania composites. First, submicron titania particles are prepared via surfactant-free sol-gel method using TiCl4 as precursor. These particles are subsequently used as inorganic fillers (or reinforcement) for thermally cured epoxy polymers. Epoxy-titania composites are prepared via mechanical mixing of titania particles with liquid epoxy resin and subsequently curing the mixture with an aliphatic diamine. The amount of titania particles integrated into epoxy matrix is varied between 2.5 and 10.0 wt.% to investigate the effect of sub-micron titania particles on thermal and mechanical properties of epoxy-titania composites. These composites are characterized by X-ray photoelectron (XPS) spectroscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric (TG), and mechanical analyses. It is found that sub-micron titania particles significantly enhance the glass transition temperature (>6.7%), thermal oxidative stability (>12.0%), tensile strength (>21.8%), and Young's modulus (>16.8%) of epoxy polymers. Epoxy-titania composites with 5.0 wt.% sub-micron titania particles perform best at elevated temperatures as well as under high stress.

4-(4-Nitro-phen-oxy)butanol.

The crystal structure of the title compound, C(10)H(13)NO(4), features inter-molecular O-H⋯O(nitro) hydrogen bonding, which links mol-ecules into supra-molecular chains running parallel to the bc diagonal. There is also π-π stacking between 4-nitro-phenyl groups, the inter-planar distance between the nitro-benzene rings being 3.472 (2) Å.

Study of Proton Transport in Diethylmethylammonium Poly[4-styrenesulfonyl(trifluoromethylsulfonyl)imide]-Based Composite Membranes with Triflic Acid and Diethylmethylamine-Rich Compositions.

The study highlights the effect of acid- and base-rich conditions on the proton dynamics of diethylmethylammonium poly[4-styrenesulfonyl(trifluoromethylsulfonyl)imide, [DEMA][PSTFSI], a polymerized protic ionic liquid designed as a polymer electrolyte for nonhumidified polymer electrolyte membrane fuel cells. Different proportions of triflic acid (HTf) and diethylmethylamine (DEMA) were added to the pristine polymer. The thermal analysis of the mixtures revealed that the addition of the base increases the glassy/amorphous nature of the polymer; however, HTf plasticizes the polymer and lowers the Tg value, so that it falls outside of the differential scanning calorimetry-studied temperature range. 50 mol % doping of the HTf contents increases the conductivity upto 0.952 mS cm-1, and 50 mol % DEMA mixture has a conductivity of 0.169 mS cm-1 at 100 °C. Vogel-Tamman-Fulcher fitting of the ionic conductivities of the doped systems suggested that the ionic conductivities are completely decoupled from segmental motion of the polymer. A combination of Fourier transform infrared and static NMR studies demonstrated that HTf-added polymer composites show conduction via Grotthuss and vehicular mechanisms, while DEMA-added polymer composites show predominantly a Grotthuss mechanism by developing the aggregates of proton and added base.

4-Nitro-phenyl 1-naphthoate.

In the title compound, C(17)H(11)NO(4), the dihedral angle between the two benzene rings is 8.66 (3)°. The nitro group is twisted by 4.51 (9)° out of the plane of the aromatic ring to which it is attached. The presence of inter-molecular C-H⋯O contacts in the crystal structure leads to the formation of chains along the c axis.

1,10-Bis(4-nitro-phen-oxy)deca-ne.

The title compound, C(22)H(28)N(2)O(6), crystallizes with four half-mol-ecules in the asymmetric unit: each mol-ecule is located about a crystallographic inversion centre. The central methyl-ene groups of two mol-ecules are disordered over two sets of equally occupied sites. The crystal packing is characterized by sheets of mol-ecules parallel to (14).

4-Methyl-benzyl 4-amino-benzoate.

The dihedral angle between the two benzene rings in the title compound, C(15)H(15)NO(2), is 65.28 (12)°. The crystal structure is stabilized by N-H⋯N and N-H⋯O hydrogen bonds, leading to the formation of supra-molecular chains along the a-axis direction.

2-{5-[2-(4-Nitro-phen-oxy)phen-yl]-1-phenyl-1H-pyrazol-3-yl}phenol.

In the title compound, C(27)H(19)N(3)O(4), the phenol and pyrazole rings are almost coplanar [dihedral angle = 0.95 (12)°] due to an intra-molecular O-H⋯N hydrogen bond, whereas the phenyl ring is tilted by 40.81 (7)° with respect to the plane of the pyrazole ring. The aromatic ring with a nitro-phen-oxy substituent makes a dihedral angle of 54.10 (7)° with the pyrazole ring.

4-Nitro-phenyl 2-methyl-benzoate.

The title compound, C(14)H(11)NO(4), crystallizes with two mol-ecules in the asymmetric unit. The major conformational difference between these two mol-ecules is the dihedral angle between the aromatic rings, namely 36.99 (5) and 55.04 (5)°. The nitro groups are coplanar with the phenyl rings to which they are attached, the O-N-C-C torsion angles being -1.9 (3) and 1.0 (3)° in the two mol-ecules.

4-(4-Nitro-phenoxy)biphen-yl.

The two phenyl rings of the biphenyl unit of the title compound, C(18)H(13)NO(3), are almost coplanar [dihedral angle 6.70 (9)°]. The nitro-phenyl ring, on the other hand, is significantly twisted out of the plane of the these two rings, making dihedral angles of 68.83 (4)° with the middle ring and 62.86 (4)° with the end ring. The nitro group is twisted by 12.1 (2)° out of the plane of the phenyl ring to which it is attached.

6-(4-Nitro-phen-oxy)hexa-nol.

The title compound, C(12)H(17)NO(4), features an almost planar mol-ecule (r.m.s. deviation for all non-H atoms = 0.070 Å). All methyl-ene C-C bonds adopt an anti-periplanar conformation. In the crystal structure the mol-ecules lie in planes parallel to (12) and the packing is stabilized by O-H⋯O hydrogen bonds.

4,4'-(Hexane-1,6-diyldi-oxy)dianiline.

The complete molecule of the title compound, C(18)H(24)N(2)O(2), is generated by a crystallographic inversion centre. The torsion angles in the hexa-methyl-ene chain are consistent with an anti-periplanar conformation, whereas the conformation of the O-CH(2)-CH(2)-CH(2) unit is gauche. The three-dimensional crystal packing is stabilized by N-H⋯O and N-H⋯N hydrogen bonding.

1,5-Bis(4-nitro-phen-oxy)penta-ne.

The title compound, C(17)H(18)N(2)O(6), crystallizes with two mol-ecules in the asymmetric unit. In both molecules, one of the C-C bonds of the penta-methyl-ene chain connecting the two aromatic rings is in a trans conformation and another displays a gauche conformation. The aromatic rings within each mol-ecule are nearly coplanar [dihedral angles = 3.36 (9) and 4.50 (9)°] and the nitro groups are twisted slightly out of the planes of their attached rings [dihedral angles = 8.16 (3)/6.6 (2) and 4.9 (4)/3.8 (3)°].

N-(3-Nitro-benzyl-idene)aniline.

In the title compound, C(13)H(10)N(2)O(2), a Schiff base derivative, the dihedral angle between the two aromatic rings is 31.58 (3)°. The C=N double bond is essentially coplanar with the nitro-phenyl ring. The torsion angle of the imine double bond is 175.97 (13)°, indicating that the C=N double bond is in a trans configuration. The crystal structure is stabilized by C-H⋯O contacts and π-π inter-actions (centroid-centroid distances of 3.807 and 3.808Å).

1,4-Bis(4-amino-phen-oxy)benzene.

The title compound, C(18)H(16)N(2)O(2), is a precusor for the synthesis of polyimides. The mol-ecule is located on a crystallographic inversion center and the terminal amino-phen-oxy rings are almost perpendicular to the central benzene ring with a dihedral angle of 85.40 (4)°. The mol-ecular conformation is stabilized by N-H⋯O and N-H⋯N inter-molecular hydrogen-bonding inter-actions.

1,2-Bis(4-amino-phen-oxy)ethane.

The mol-ecule of the title compound, C(14)H(16)N(2)O(2), is located on a crystallographic twofold rotation axis. The central O-C-C-O bridge adopts a gauche conformation. One of the amine H atoms is disordered over two equally occupied positions. The crystal structure is stabilized by N-H⋯O and N-H⋯N hydrogen bonds.

1,1,1,3,3,3-Hexafluoro-2,2-bis-[4-(4-nitro-phen-oxy)phen-yl]propane.

In the title compound, C(27)H(16)F(6)N(2)O(6), the nitro groups are almost coplanar with the aromatic rings to which they are attached [dihedral angles = 3.5 (5) and 6.2 (3)°]. The dihedral angles between adjacent aromatic rings are 78.07 (8) and 71.11 (8)° for nitro-phen-yl/phenyl and 69.50 (8)° for phen-yl/phenyl. An inter-molecular C-H⋯π inter-action seems to be effective in the stabilization of the structure.

N-[4-(4-Nitro-phen-oxy)phen-yl]propionamide.

The title compound, C(15)H(14)N(2)O(4), is an important inter-mediate for the synthesis of thermotropic liquid crystals. The dihedral angle between the two aromatic rings is 84.29 (4)°. An N-H⋯O hydrogen bond connects the mol-ecules into chains running along the b axis. In addition, the crystal packing is stabilized by weak C-H⋯O hydrogen bonds.