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Near-infrared absorbing azaborondipyrromethenes (azaBODIPYs), 1, 2, and 3, tethered with phenothiazine (PTZ) and/or naphthalene at 1,7 and/or 3,5 positions, were synthesized and photoinduced energy (PEnT) and electron (PET) events occurring within these compounds were systematically studied. Steady-state fluorescence studies have shown that, when the phenothiazine moiety, in 1 and 2, was selectively excited, the fluorescence of the PTZ and azaBODIPY was quenched, indicating the occurrence of PET from the singlet excited phenothiazine to the azaBODIPY. On the other hand, when the naphthalene moiety in 3 was excited, the emission of the naphthalene was observed to be quenched with the concomitant appearance of the azaBODIPY emission indicating the display of PEnT from ¹naphthalene* to the azaBODIPY. Interestingly, in the case of 1, selective excitation of naphthalene resulted in the quenching of both the naphthalene and azaBODIPY emissions, indicating the possibility of PEnT from ¹naphthalene* to azaBODIPY followed by a tandem PET from the ground state of the phenothiazine moiety to the azaBODIPY. The present work showed the synthetic scope of introducing two different chromophores onto the azaBODIPY platform to produce panchromatic dyes and systematically revealed the significance of the individual constituents, PTZ and naphthalene as electron and energy donors, and azaBODIPY as an excited state energy or electron receiver in the PET and PEnT processes.

Polyazomethine-type conjugated polymers were synthesized by Schiff-base reaction. One was poly(PZ-PBI) with alternating phenothiazine (PZ) and azomethine units (-C = N-), and the other was poly(CZ-PBI) comprising alternating carbazole (CZ) and azomethine groups. Conjugated polymers exhibited improved solubility in common organic solvents due to alkyl side chains on phenothiazine and carbazole rings as well as polar azomethine groups in main chains. Single- and double-layer PLEDs were fabricated. Their electroluminescent properties were studied from the viewpoint of polymer structure vs. emission color and efficiency.

Novel octa-phenotiazine, octa-benzoazepine and octa-carbazole substituted magnesium(II) (MgPz-I-III) and zinc(II) (ZnPz-I-III) porphyrazines were synthesized from 2,3-bis[6-(4a,10a-dihydro-phenothiazin-10-yl)-hexylsulfanyl]-but-2-enedinitrile (5), 2,3-bis [6-(4a,11a-dihydro-dibenzo[b,f]azepin-5-yl)-hexysulfan-yl]-but-2-enedinitrile (8) and 2,3-bis(6-carbazol-9-yl-hexylsulfanyl)-but-2-enedinitrile (10), respectively. These dinitrile derivatives 5, 8 and 10 were also prepared by the reaction of 1,2-dicyano-1,2-ethylenedithiolate di-sodium salt (4) with 10-(6-bromohexyl)-10H-phenothiazine (3), 5-(6-bromohexyl)-5H-diben-zo[b,f]azepine (7) and 9-(6-bromo-hexyl)-9H-carbazole (9), respectively. Porphyrazino-zinc(II) complexes were synthesized by one-step reaction using Zn(BuO)${}_{\mathrm{\text{2}}}$ as a template agent. All the novel compounds were characterized by elemental analysis and different spectroscopic methods such as ${}^{\mathrm{\text{1}}}$H NMR, ${}^{\mathrm{\text{13}}}$C NMR, FT-IR, UV-Vis and mass. The photochemical properties including photodegradation and singlet oxygen generation for magnesium(II) and zinc (II) porphyrazine complexes were studied in dimethylsulfoxide solutions for determination of their photosensitizer behaviors.

Self-assembled donor–acceptor conjugates featuring zinc phthalocyanine carrying four entities of peripheral phenothiazine entities, (PTZ)${}_{\mathrm{\text{4}}}$ZnPc, axially coordinated to either phenyl imidazole or pyridine functionalized fulleropyrrolidine (C${}_{\mathrm{\text{60}}}$Im or C${}_{\mathrm{\text{60}}}$Py) has been newly designed, synthesized and characterized. Due to the direct connectivity of the phenothiazine entities to the ZnPc $\pi$-system, efficient charge transfer type interactions suppressing fluorescence of ZnPc in (PTZ)${}_{\mathrm{\text{4}}}$ZnPc was observed. Axial coordination of C${}_{\mathrm{\text{60}}}$Im or C${}_{\mathrm{\text{60}}}$Py to the metal center of (PTZ)${}_{\mathrm{\text{4}}}$ZnPc served as an electron acceptor in the conjugates. Optical absorption studies revealed stable complex formation wherein the evaluated binding constants $K$ were found to be 3.9 × 10${}^{\mathrm{\text{4}}}$ M${}^{\mathrm{\text{-1}}}$ for (PTZ)${}_{\mathrm{\text{4}}}$ZnPc:ImC${}_{\mathrm{\text{60}}}$ and 3.3 × 10${}^{\mathrm{\text{4}}}$ M${}^{\mathrm{\text{-1}}}$ for (PTZ)${}_{\mathrm{\text{4}}}$ZnPc:PyC${}_{\mathrm{\text{60}}}$ conjugates with 1:1 molecular stoichiometry. Computational studies performed at the HF/[6-311G(d,p) for H, C, and N, and 6-311G(2df) for S and Zn] level revealed stable structures of the conjugates. The evaluated center-to-center and edge-to-edge distances for the (PTZ)${}_{\mathrm{\text{4}}}$ZnPc:ImC${}_{\mathrm{\text{60}}}$ were 13.6 and 10.4 Å, while for the (PTZ)${}_{\mathrm{\text{4}}}$ZnPc:PyC${}_{\mathrm{\text{60}}}$ conjugate these distances were 10.2 and 7.3 Å. That is, the C${}_{\mathrm{\text{60}}}$ was about 3̃ Å closer to ZnPc in the latter conjugate. From the free-energy calculations, photoinduced electron transfer from the ${}^{\mathrm{\text{1}}}$ZnPc* to fullerene within the conjugates was established to be an exothermic process, however, a hole transfer from ZnPc${}^{•+}$ to peripheral PTZ was found to be energetically an uphill process. From femtosecond transient absorbance studies, occurrence of photoinduced charge separation in (PTZ)${}_{\mathrm{\text{4}}}$ZnPc:ImC${}_{\mathrm{\text{60}}}$ was found to be weak due to the competing charge transfer interactions within the (PTZ)${}_{\mathrm{\text{4}}}$ZnPc and longer donor–acceptor distance while in the case of the (PTZ)${}_{\mathrm{\text{4}}}$ZnPc:PyC${}_{\mathrm{\text{60}}}$ conjugate, electron transfer occurred competitively to yield radical ion-pairs. From nanosecond transient spectroscopy, lifetime of the (PTZ)${}_{\mathrm{\text{4}}}$ZnPc${}^{•+}$:PyC${}_{\mathrm{\text{60}}}^{•-}$ charge separated state was found to be in the 200 ns range, revealing charge stabilization to some extent.

We report two corrole based donor–acceptor (D–A) dyads, Cbz-Cor and Ptz-Cor to understand the energy/electron transfer reactions. In these D–A systems, the donor, either carbazole (Cbz) or phenothiazine (Ptz), is covalently connected at the meso-phenyl position of 10-(phenyl)-5,15-bis-(pentafluorophenyl)corrole (Ph-Cor) by C–N linkage. Both the dyads were characterized by ¹H NMR, MALDI-TOF MS, UV-vis, electrochemical, computational methods, study state fluorescence and TCSPC techniques. A comparison of absorption spectra with their reference monomeric compounds (Cbz-Ph, Ptz-Ph and Ph-Cor) revealed minimal ground-state interactions between chromophores in both dyads. Fluorescence studies suggested that singlet–singlet energy transfer from ¹Cbz* to corrole is the major photochemical pathway in the Cbz-Cor dyad with a quenching efficiency of $\sim$99%. Detailed analysis of the data suggests that Forster’s dipole–dipole mechanism does not adequately explain this energy transfer. However, at a 410 nm excitation, florescence quenching is detected in Ptz-Cor (49%) supporting a photo induced electron transfer (PET) process from the ground state of PTZ to the excited state of corrole macrocycle. The electron-transfer rates ($k_{ET})$ of Ptz-Cor are found in the range $0.6\times 10^7$ to $1.24\times 10^8{\mathrm{\text{s}}}^{-1}$ and are concluded to be solvent dependent.

In this work, the impact of extending $\pi$-bridge and the adsorption of dyes on the nanocrystalline surface of TiO₂ on photovoltaic parameters in dye-sensitized solar cells (DSSCs) has been explored. The dyes comprise phenothiazine (donor), along with benzene, furan, thiophene and selenophene ($\pi$-spacers), and cyanoacrylic acid anchoring group (acceptor). The dye geometries, charge transference, and electronic characteristics were investigated using density functional theory (DFT). The impact of extended $\pi$-bridge in conjugated systems was explored in dyes along with dyes adsorbed on TiO₂ nanocrystalline surface (dye@TiO${}_2)$. For the architecture D–$\pi$–A in this work, the dyes are effectively adsorbed on the TiO₂ nanocrystalline surface. The energy gap between HOMO and LUMO (HLG), ionization potential (IP), reorganization energies ($\lambda )$, electron affinity (EA), photovoltaic parameters, adsorption energy (AE), and total density of state (TDOS) are simulated theoretically. Additionally, our investigation illustrates that the studied organic photosensitizer dyes may have improved photovoltaic characteristics and are suitable applicants for efficient charge transportation in organic electronic materials.