1. Photophysical, electrochemical and solid state properties of diketopyrrolopyrrole based molecular materials: importance of the donor group

JoydeepDhar, N. Venkatramaiah, Anitha A. and SatishPatil

J. Mater. Chem. C, 2014, 2, 3457–3466

Received 15th November 2013 Accepted 4th February 2014
DOI: 10.1039/c3tc32251c

In this work, we have synthesized a series of TDPP derivatives with different alkyl groups such as n-hexyl (−C6H13) 3a, 2-ethylhexyl (-(2-C2H5)C6H12) 3b, triethylene glycol mono methyl ether (-(CH2CH2O)3cH3, TEG) 3c, and octadodecyl (-(8-C8H17)C12H22) 3d. N,N dialkylation of thiophene-diketopyrrolopyrrole (TDPP, 1) strongly influences its solubility, solid state packing, and structural order. These materials allow us to explicitly study the influence of alkyl chain on solid state packing and photophysical properties. TDPP moiety containing two different alkyl groups 3e (TEG and 2-ethylhexyl) and 3f (TEG and n-hexyl) were synthesized for the first time. The absorption spectra of all derivatives exhibited a red shift in solid state when compared to their solution spectra. The type of alkyl chains leads to change in the optical band gaps in solid state. The fluorescence study reveals that TDPP derivatives have strong π–π interaction in the solid state and the extent of bathochromic shift is due to combination of intramolecular interaction and formation of aggregates in solid state. This behavior strongly depends on the nature of alkyl chain. The presence of strong C–H···O inter chain interactions and CH−π interactions in solid state exhibits strong influence on the photophysical properties of TDPP chromophore.

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2. Influence of Side-Chain on Structural Order and Photophysical Properties in Thiophene Based Diketopyrrolopyrroles: A Systematic Study

Mallari A. Naik , N. Venkatramaiah , Catherine Kanimozhi , and Satish Patil

J. Phys. Chem. C, 2012, 116 (50), pp 26128–26137

DOI: 10.1021/jp306365q
Publication Date (Web): November 14, 2012
Copyright © 2012 American Chemical Society

In this work, we have synthesized a series of TDPP derivatives with different alkyl groups such as n-hexyl (−C6H13) 3a, 2-ethylhexyl (-(2-C2H5)C6H12) 3b, triethylene glycol mono methyl ether (-(CH2CH2O)3cH3, TEG) 3c, and octadodecyl (-(8-C8H17)C12H22) 3d. N,N dialkylation of thiophene-diketopyrrolopyrrole (TDPP, 1) strongly influences its solubility, solid state packing, and structural order. These materials allow us to explicitly study the influence of alkyl chain on solid state packing and photophysical properties. TDPP moiety containing two different alkyl groups 3e (TEG and 2-ethylhexyl) and 3f (TEG and n-hexyl) were synthesized for the first time. The absorption spectra of all derivatives exhibited a red shift in solid state when compared to their solution spectra. The type of alkyl chains leads to change in the optical band gaps in solid state. The fluorescence study reveals that TDPP derivatives have strong π–π interaction in the solid state and the extent of bathochromic shift is due to combination of intramolecular interaction and formation of aggregates in solid state. This behavior strongly depends on the nature of alkyl chain. The presence of strong C–H···O inter chain interactions and CH−π interactions in solid state exhibits strong influence on the photophysical properties of TDPP chromophore.

 

3. Femtogram Detection of Explosive Nitroaromatics: Fluoranthene-Based Fluorescent Chemosensors

Dr. N. Venkatramaiah, Shiv Kumar, Prof. Satish Patil*

Chemistry – A European Journal Volume 18, Issue 46, pages 14745–14751, November 12, 2012

Herein we report a novel fluoranthene-based fluorescent fluorophore 7,10-bis(4-bromophenyl)-8,9-bis[4-(hexyloxy)phenyl]fluoranthene (S3) and its remarkable properties in applications of explosive detection. The sensitivity towards the detection of nitroaromatics (NACs) was evaluated through fluorescence quenching in solution, vapor, and contact mode approaches. The contact mode approach using thin-layer silica chromatograp- hic plates exhibited a femtogram (1.15 fg cm−2) detection limit for trinitrotoluene (TNT) and picric acid (PA), whereas the solution-phase quenching showed PA detection at the 2–20 ppb level. Fluorescence lifetime measurements revealed that the quenching is static in nature and the quenching process is fully reversible. Binding energies between model binding sites of the S3 and analyte compounds reveal that analyte molecules enter into the cavity created by substituted phenyl rings of fluoranthene and are stabilized by strong intermolecular interactions with alkyl chains. It is anticipated that the sensor S3 could be a promising material for the construction of portable optical devices for the detection of onsite explosive nitroaromatics.

4. Diketopyrrolopyrrole–Diketopyrrolopyrrole-Based Conjugated Copolymer for High-Mobility Organic Field-Effect Transistors

Catherine Kanimozhi , Nir Yaacobi-Gross , Kang Wei Chou §, Aram Amassian §, Thomas D. Anthopoulos *, and Satish Patil *

J. Am. Chem. Soc., 2012, 134 (40), pp 16532–16535
DOI: 10.1021/ja308211n
Publication Date (Web): September 28, 2012
Copyright © 2012 American Chemical Society

In this communication, we report the synthesis of a novel diketopyrrolopyrrole–diketopyrrolopyrrole (DPP–DPP)-based conjugated copolymer and its application in high-mobility organic field-effect transistors. Copolymerization of DPP with DPP yields a copolymer with exceptional properties such as extended absorption characteristics (up to 1100 nm) and field-effect electron mobility values of >1 cm2 V–1 s–1. The synthesis of this novel DPP–DPP copolymer in combination with the demonstration of transistors with extremely high electron mobility makes this work an important step toward a new family of DPP–DPP copolymers for application in the general area of organic optoelectronics.

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5.Fluoranthene based fluorescent chemosensors for detection of explosive nitroaromatics

N. Venkatramaiah , Shiv Kumar and Satish Patil

Chem. Commun., 2012,48, 5007-5009
DOI: 10.1039/C2CC31606D

A novel fluoranthene based fluorescent chemosensor for the detection of picric acid (PA) at the parts per billion (ppb) level was evaluated. Static fluorescence quenching was the dominant process by intercalative π–π interaction between fluoranthene (S1) and nitroaromatics.

6.Diketopyrrolopyrrole-based conjugated polymers and small molecules for organic ambipolar transistors and solar cells (pages 4241-4260)

Mallari A. Naik and Satish Patil

Journal of Polymer Science, Part A: Polymer Chemistry, Volume 51, Issue 20, pages 4241–4260, October 2013
Article first published online: 10 JUL 2013 | DOI: 10.1002/pola.26843

The present work discusses the development and use of diketopyrrolopyrrole (DPP)-based conjugated polymers in organic electronic research. The figure gives glimpses of some important DPP based polymeric systems. The device architecture in the bottom left corner shows that DPP polymers are used as donor and fullerene based materials as acceptor. The energy level diagram located in the center shows how the split in band gap takes place upon absorbing sunlight. All these major observations and achievements made from the use of DPP by various research groups are summarized in the highlight

 

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7. Enhancing Surface Coverage and Growth in Layer-by-Layer Assembly of Protein Nanoparticles

Vaishakhi Mohanta and Satish Patil

Langmuir, 2013, 29 (43), pp 13123–13128
DOI: 10.1021/la401731a
Publication Date (Web): August 1, 2013
Copyright © 2013 American Chemical Society

Thin films of bovine serum albumin (BSA) nanoparticles are fabricated via layer-by-layer assembly. The surface of BSA nanoparticles have two oppositely acting functional groups on the surface: amine (NH2) and carboxylate (COO−). The protonation and deprotonation of these functional groups at different pH vary the charge density on the particle surface, and entirely different growth can be observed by varying the nature of the complementary polymer and the pH of the particles. The complementary polymers used in this study are poly(dimethyldiallylammonium chloride) (PDDAC) and poly(acrylic acid) (PAA). The assembly of BSA nanoparticles based on electrostatic interaction with PDDAC suffers from the poor loading of the nanoparticles. The assembly with PAA aided by a hydrogen bonding interaction shows tremendous improvement in the growth of the assembly over PDDAC. Moreover, the pH of the BSA nanoparticles was observed to affect the loading of nanoparticles in the LbL assembly with PAA significantly.