WP1.1: Synthesis of N-heterotriangulene (NHT)-Diketopyrollopyrrole (DPP) conjugated D-A materials
-Results: (i) Synthesis of the NHT acceptor precursor. (i) Two-fold Ullmann coupling of methylanthranilate with methyl-2-iodobenzoate gave the key precursor as triester, (ii) iodination of the precursor in presence of silver sulphate in ethanol yielded the tri-iodinated derivative and (iii) saponification, followed by the cyclization of the in situ generated acyl chloride, employing standard Friedel-Craft’s acylation conditions using SnCl4 as a Lewis acid furnished NHT. (ii) Synthesis of the thiophene appended DPP donor precursor. (i) Modified Reformatsky reaction between succinate ester and 2-thiophenecarbonitrile in presence of t-BuOK and t-amyl alcohol, (ii) N-alkylation at the amide nitrogens using 1-iododhexane and 1-iodooctane yielded soluble dialkyl-DPP-thiophene conjugates, (iii) Bromination with N-bromosuccinimide (NBS), followed by stannylation using t-butyl tin chloride afforded the donor subunit.
-As part of our collaboration with Prof. Dario Pasini, University of Pavia, Italy I was successful in synthesising novel donor-acceptor-donor triad sandwiching DPP between naphthothiophene donors. (i) Synthesis of the naphthothiophene (NT) donor precursor. (i) 3-thiopheneacetic acid to generate NT-acid, (ii) the acid was esterified in presence of a base such as K2CO3, (iii) bromination of the ester using NBS in CHCl3 afforded monobrominated NT derivative which was subsequently stannylated using t-butyl tin chloride in presence of LDA in THF to afford the stannyl derivative of the donor subunit.
-(ii) Synthesis of the thiophene appended DPP acceptor precursor. (i) Modified Reformatsky reaction between succinate ester and 2-thiophenecarbonitrile in presence of t-BuOK and t-amyl alcohol, (ii) N-alkylation at the amide nitrogens using 1-iododhexane and 1-iodooctane yielded soluble dialkyl-DPP-thiophene conjugates, (iii) Bromination with NBS in CHCl3 yielded the dibrominated DPP acceptor subunit.
-Furthermore, Pd-catalyzed Stille cross-coupling of NT-SnBu3 (donor) and DPP-Br2 (acceptor) under standard conditions afforded the symmetrical donor-acceptor-donor triad (NT-DPP-NT).
WP1.2: Photophysical and electrochemical measurements of D-A-D conjugate:
-Results: (i) The preliminary photophysical measurements such as absorption, fluorescence, fluorescence lifetime and quantum yield measurements of novel NT-DPP-NT conjugate was carried out in dichloromethane. (ii) Concentration dependent measurements were performed to estimate the extinction coefficient of the novel donor-acceptor-donor triad. (iii) Electrochemical measurements such as cyclic voltammetry and spectroelectrochemical measurements. (iv) To map the frontier molecular orbitals and electron density of the highest occupied and lowest unoccupied molecular orbitals theoretical calculations were performed. The results obtained as part of the proposal will be disseminated in the form of publication in peer reviewed science journals: (i) a first draft of the NT-DPP-NT triad manuscript is submitted to the supervisor which has three collaborators, 1. Prof. Dario Pasini, University of Pavia, Italy,(2) Prof. Steven Davies, School of Chemistry, University of Nottingham, UK and (3)Dr. Mahesh Hariharan, School of Chemistry, IISER-TVM, Kerala, India., (ii) A tutorial review entitled Rational Design Principles for Highly Efficient Small Molecular Fullerene Free Acceptors is under preparation, (iii) the manuscript compiling the results obtained for water soluble DPP polymers is under preparation, (iv) a book chapter entitled Chirality in Hierarchical supramolecular architectures is accepted for publication.
