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Understanding the structure‐property relationship is one of the critical factors in the practical design of organic small molecules for bulk heterojunction organic solar cells (BHJ‐OSCs). In this study, we designed and synthesized two low‐band‐gap organic small molecule donors, TRh and PhRh. To study the effect of the π‐conjugated spacer, the A‐π‐D‐π‐A architecture was constructed with an efficient dithienopyrrole donor (D) and rhodanine acceptor (A) units. Two types of π‐conjugated spacers, thiophene in TRh and phenyl in PhRh, are used to fine‐tune the various properties. A detailed investigation of the effect of π‐conjugated spacers on optoelectronic, thermal, and photovoltaic properties have carried out. TRh is planar, more conjugated, has a more prolonged absorption wavelength and leads to a low band gap of 1.48 eV. DFT studies demonstrate that TRh has lower BLA (Bond length alternation) and has more quinoid structure than PhRh. PhRh is thermally more stable than TRh. PhRh displayed a high glass transition temperature (Tg) at 193 °C and a 5% decomposition temperature at 402 °C. The inverted device architecture of BHJ‐OSCs blended with PC71BM displayed the PCE of 2.78% for TRh and 1.10% for PhRh. TRh : PC71BM blend exhibits higher hole and electron mobilities than PhRh : PC71BM blend. [ABSTRACT FROM AUTHOR]

Three new terpyridine appended pyrene derivatives (Pyr-Tp, Pyr-Ph-Tp, and Pyr-Bp-Tp) have been synthesized by condensation and Suzuki-Miyaura reaction. The photo-physical, electro-chemical and thermal properties of these compounds have been investigated in detail. DFT studies have been carried out to understand the structure-property relationships at the molecular level. Synthesized fluorophores displayed high quantum yield (70-96%) of fluorescence due to triplet to singlet intramolecular energy transfer, delayed fluorescence and positive solvatochromism indicating the presence of intra-molecular charge transfer excited state. In addition, they have high thermal decomposition temperature (Td: 390-450°C), melting temperature (Tm: 180-220°C) and further with suitable oxidation and reduction potentials makes them favourable molecules for OLED fabrications. [ABSTRACT FROM AUTHOR]

A systematic study has been conducted for the regioselective halogenation of 2H‐chromenones to prepare 3‐halo‐2H‐chromenones, 4‐substituted 3‐halo‐2H‐chromenones and 3‐(2‐haloacetyl)‐2H‐chromenones. Commercially available NaCl/NaBr has been used as halogen source and oxone as an oxidant to produce the compounds. Further, the method has been successfully applied for the preparation of pharmaceutically important halogenated 2H‐chromenone natural products. The present approach is simple, economically viable and provided the target compounds with good yields. [ABSTRACT FROM AUTHOR]

We have designed A-D--D-A type three new small molecular donor materials denoted as FD-IND, FD-DCV and FD-NBR, which have been synthesised and their photo-physical, electrochemical and thermal properties explored. The synthesised materials have fluorene as "-spacer," dithieonopyrrole as "Donor" (D) and various "Acceptor" (A) units are 1,3-indanedione (IND), dicyanovinylene (DCV) and N-butyl rhodanine (NBR). All these three materials have good solubility (~30 mg/mL) in most common organic solvents and have relatively broad absorption in the visible region covering the range of 300-650 nm with two primary absorption bands. The absorption bands located at shorter wavelength region are ascribed to a localized aromatic -* transition of the A-D--D-A system, while the bands at longer wavelength are mainly attributed to an ICT transition. All the compounds exhibit excellent thermal stabilities in the range of 260-373°C. Cyclic voltammetry data provided HOMO values as -5.26, -5.32 and -5.32 eV for FD-NBR, FD-DCV and FD-IND respectively. LUMO values estimated from HOMO values and optical band gap are -3.27, -3.22 and -3.37 eV for FD-NBR, FD-DCV and FD-IND respectively. Therefore, these are potential molecules for organic solar cells. [ABSTRACT FROM AUTHOR]

An efficient synthetic protocol was developed for the formation of 2‐allylidene 1,3‐diones in very good yields via [3,3]‐sigmatropic rearrangement of O‐propargyl β‐enones. Good yields of highly functionalized substituted furan derivatives were synthesized from O‐propargyl β‐enones under gold‐catalysis via intramolecular cycloisomerisation. We have developed an efficient method for synthesis of several new 2‐allylidene 1,3‐diones in very good yields under thermal condition via [3,3]‐sigmatropic rearrangement. Further, O‐propargyl β‐enones were directly converted to the corresponding substituted furan derivatives under gold‐catalysis via cyclo‐isomerisation. Moderate to good yields of substituted furan derivatives were generated with significant molecule complexity in one‐pot. [ABSTRACT FROM AUTHOR]

This paper describes a mild phenyliodine diacetate mediated method for selective chlorination, bromination, and iodination of indole C–H bonds using sodium halide as a source for analogous halogenations. The combination of NaX and phenyliodine diacetate provides an invincible system for halogenation of indoles. This protocol was compatible with a wide array of indole substrates and provides straight forward access to potential halogenated arenes. [ABSTRACT FROM AUTHOR]

Four conjugated small molecules (2TPzDP, 3TPzDP, 2TTPzDP, and 3TTPzDP) were synthesized consisting of a 3,7‐diphenyldipyrrolo[2,3‐b : 2′,3′‐e]pyrazine‐2,6(1H,5H)‐dione core end‐capped with either 2‐alkylthiophene (2T), 3‐alkylthiophene (3T), 2‐alkyl‐2,2′‐bithiophene (2TT) or 3‐alkyl‐2,2′‐bithiophene (3TT). All the compounds exhibited two absorption bands, one in the ultraviolet (λmax=307–347 nm) and other in the visible (λmax=582–631 nm) region. The HOMO/LUMO values for 2TPzDP, 3TPzDP, 2TTPzDP, and 3TTPzPDP were measured as −5.68/−3.97, −5.67/−3.97, −5.49/−4.01, and −5.45/−3.99 eV, respectively, which are well matched with regioregular poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) (−5.0/−3.0 eV) to act as n‐type semiconductors for photovoltaic applications. Fluorescence quenching experiments revealed an efficient charge transfer between the donor material P3HT and the synthesized acceptor molecules. The Td values of all the four compounds are in the range of 355–391 °C representing their good thermal stability. These properties evaluated are found to be excellent for the fabrication of bulk heterojunction organic solar cells using P3HT. Conjugation: Four new thiophene‐endcapped 3,7‐diphenyldipyrrolo[2,3‐b : 2′,3′‐e]pyrazine‐2,6(1H,5H)‐diones 2TPzDP, 3TPzDP, 2TTPzDP, and 3TTPzDP with PzDP as the core building block and alkylthiophene or alkyl‐2,2′‐bithiophene moieties as end capping units are synthesized. The good optical properties, suitable HOMO/LUMO energy levels, and excellent Td values portray them as good candidates as small molecule non‐fullerene acceptors for the realization of highly efficient BHJOSCs. [ABSTRACT FROM AUTHOR]