The energy conversion efficiency of dye-sensitized solar cells derived from organic dye molecules has seen immense interest recently. In this work, we report a series of organic donor molecules with enhanced energy conversion efficiency using π-spacers and cyanoacrylic acid as an anchoring group (2−6). Density functional theory (DFT) and timedependent DFT calculations of these molecules have been performed to examine their electronic structures and absorption spectra before and after binding to the semiconductor titanium dioxide surface. The computational results suggest that dyes 4 and 6 have a larger driving force (ΔG inject = −1.66 and −1.80 eV, respectively) and light-harvesting efficiency (LHE = 0.99) in the series of donor molecules studied. Thus, these dyes should possess a larger short-circuit photocurrent density (J sc ) compared to the other examined dyes. The reported ΔG inject (−1.62 eV) and LHE (0.98) for compound 1, calculated with the same level of theory, were lower than those of the designed 4 and 6 dyes. Furthermore, the DFT calculations showed that the open-circuit photovoltage (V oc ) is improved with the vertical dipole moment and number of photoinjected electrons for 4 and 6. Dyes 4 and 6 are expected to exhibit high solar-energy-to-electricity conversion.

We have reported a number of new metal-free organic dyes (2-6) that have cyclic asymmetric benzotripyrrole derivatives as donor groups with peripheral nitrogen atoms in the ring, fluorine and thiophene groups as π-spacers, and a cyanoacrylic acid acceptor group. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were employed to examine the influence of the position of the donor nitrogen atom and π-conjugation on solar cell performance. The calculated electron-injection driving force (ΔG inject), electron-regeneration driving force (ΔG regen), light-harvesting efficiency (LHE), dipole moment (μ normal), and number of electrons transferred (∆q) indicate that dyes 3, 4, and 6 have significantly higher efficiencies than reference dye 1, which exhibits high efficiency. We also extended our comparison to some other reported dyes, 7-9, which have a donor nitrogen atom in the middle of the ring system. The computed results suggest that dye 6 possesses a higher incident photon to current conversion efficiency (IPCE) than reported dyes 7-9. Thus, the use of donor groups with peripheral nitrogen atoms appears to lead to more efficient dyes than those in which the nitrogen atom is present in the middle of the donor ring system. Graphical Abstract The locations of the nitrogen atoms in the donor groups in the designed dye molecules have an important influence on DSSC efficiency.

An enantioselective aza-Friedel-Crafts reaction of 1-naphthol with isatin derived N-Boc ketimines by cinchona based bifunctional thiourea as organo-catalyst is reported. In general the derivatives of Betti base are formed in excellent enantioselectivities (95-99%) with high yields (<99%). The combination of experimental and computational studies have revealed the origin of the stereoselectivity of the aza-Friedel-Crafts reaction of 1-naphthol with isatin derived N-Boc ketimines by cinchona based bifunctional thiourea as organo-catalyst. The attractive electrostatic interactions in the Re face transition state and the deleterious lone-pair/p interactions in the Si face transition state governed the formation of Re-face as a major product in this aza Friedel-Crafts reaction. The NMR studies performed to examine the formation of the complex with 1-naphthol, isatin derived N-Boc ketimines and cinchona based bifunctional thiourea catalyst has corroborated the calculated complex geometry employed in the study.

A series of chiral polymeric Co(III) salen complexes based on a number of achiral and chiral linkers were synthesized and their catalytic performances were assessed in asymmetric hydrolytic kinetic resolution of terminal epoxides. The effect of the linker were judiciously studied and it was found that in case of chiral BINOL based polymeric salen complex 1, there was certain enrichment in catalyst reactivity and enantioselectivity of the unreacted epoxide particularly in the case of shor t as well as long chain aliphatic epoxides. Good isolated yield of the unreacted epoxide (up to 46% out of 50% theoretical yield) along with high enantioselectivity (up to >99%) were obtained in most of the cases using catalyst 1. Further studies exhibited that the catalyst 1 could retain its catalytic activity for six cycles under the present reaction conditions without any significant loss in activity and enantioselectivity. To show the practical applicability of the above synthesized catalyst we have car ried out synthesis of some potent chiral -blockers using complex 1 in moderate yield and high enantioselectivity. The DFT (M06 -L/6-31+G**//ONIOM(B3LYP/6-31G*:STO-3G)) calculations revealed that the chiral BIN OL linker influences the enantioselectivity with Co(III)salen complexes. Further, the transition state calculations show that the R-BINOL linker with (S,S)-(salen)Co(III) complex is energetically preferred over the corresponding S-BINOL linker with (S,S)-(salen)Co(III) complex for HKR of 1,2-epoxyhexane. The role of non-covalent C-H… π interaction and steric effects has been discussed to control the HKR reaction of 1,2 -epoxyhexane.