@article {45936, title = {Seeded on-surface supramolecular growth for large area conductive donor-acceptor assembly}, journal = {Chemical Communications}, volume = {51}, year = {2015}, month = {MAY}, pages = {10439-10442}, type = {Article}, abstract = {

Charge transport features of organic semiconductor assemblies are of paramount importance. However, large-area extended supramolecular structures of donor-acceptor combinations with controlled self-assembly pathways are hardly accessible. In this context, as a representative example, seeded on-surface supramolecular growth of tetrathiafulvalene and tetracyano-p-quinodimethane (TTF-TCNQ) using active termini of solution-formed sheaves has been introduced to form an extended assembly. We demonstrate for the first time, the creation of a large-area donor-acceptor assembly on the surface, which is practically very tedious, using a seeded, evaporation-assisted growth process. The excellent molecular ordering in this assembly is substantiated by its good electrical conductivity (similar to 10(-2) S cm(-1)). The on-surface assembly via both internally formed and externally added sheaf-like seeds open new pathways in supramolecular chemistry and device applications.

}, issn = {1359-7345}, doi = {10.1039/c5cc03091a}, author = {Goudappagouda and Chithiravel, Sundaresan and Krishnamoorthy, Kothandam and Gosavi, Suresh W. and Babu, Sukumaran Santhosh} } @article {46833, title = {Self-assembled helical arrays for the stabilization of the triplet state}, journal = {Angewandte Chemie-International Edition}, volume = {59}, year = {2020}, month = {JUL}, pages = {13079-13085}, type = {Article}, abstract = {

Room-temperature phosphorescence of metal and heavy atom-free organic molecules has emerged as an area of great potential in recent years. A rational design played a critical role in controlling the molecular ordering to impart efficient intersystem crossing and stabilize the triplet state to achieve room-temperature ultralong phosphorescence. However, in most cases, the strategies to strengthen phosphorescence efficiency have resulted in a reduced lifetime, and the available nearly degenerate singlet-triplet energy levels impart a natural competition between delayed fluorescence and phosphorescence, with the former one having the advantage. Herein, an organic helical assembly supports the exhibition of an ultralong phosphorescence lifetime. In contrary to other molecules, 3,6-phenylmethanone functionalized 9-hexylcarbazole exhibits a remarkable improvement in phosphorescence lifetime (\>4.1 s) and quantum yield (11 \%) owing to an efficient molecular packing in the crystal state. A right-handed helical molecular array act as a trap and exhibits triplet exciton migration to support the exceptionally longer phosphorescence lifetime.

}, keywords = {carbazole, helicity, phenylmethanone, ultralong phosphorescence, waveguiding}, issn = {1433-7851}, doi = {10.1002/anie.202005105, Early Access Date = JUN 2020}, author = {Nidhankar, Aakash D. and Goudappagouda and Kumari, Divya S. Mohana and Chaubey, Shailendra Kumar and Nayak, Rashmi and Gonnade, Rajesh G. and Kumar, G. V. Pavan and Krishnan, Retheesh and Babu, Sukumaran Santhosh} } @article {49196, title = {Solvent-free organic liquids: an efficient fluid matrix for unexplored functional hybrid materials}, journal = {Accounts of Chemical Research}, volume = {57}, year = {2024}, month = {FEB}, pages = {670-684}, type = {Review}, abstract = {

The invention of solvent-free organic liquids (SOLs) was serendipitous. However, the curiosity-driven research in the later stage delivered new soft materials with exciting optical, and optoelectronic properties along with appealing physical characteristics suitable for the futuristic applications. A slight change in the molecular design resulted in a drastic change in the physical state of molecules demonstrating monomer-like features in the bulk. The basic idea of core isolation has been successful in delivering new SOLs with attractive functional properties. The unique fluid matrix associated with SOLs offers a tremendous opportunity for making hybrid materials by simple mixing. The chance to study the fundamentally important electron transfer, energy transfer, charge transfer interactions, triplet-state emissions, and even detailed NMR experiments in the solvent-free neat state is the major attraction of SOLs. Usually, solvents and their polarity control such molecular properties, and in the case of SOLs, it avoids the use of solvents to study such fundamentally important properties. Besides, SOLs protect the triplet emitters and excited state processes involving triplet states from quenchers and make the analysis possible under ambient conditions. Our effort in this direction was focused on tuning the ground and excited state properties by transforming conventional organic molecules to SOLs and further value addition by preparing the hybrid SOLs. We developed a series of hybrid SOLs, exploring room-temperature phosphorescence, thermally activated delayed fluorescence, charge or energy transfer between donor and acceptor SOLs, selective explosive sensing, etc. A slight variation in the chemical structure or optoelectronic properties of the individual components imparted exciting optical features for the hybrid SOLs. It includes nonemissive charge transfer, tunable emission exciplex, room temperature phosphorescence, and thermally activated delayed fluorescence SOLs. The liquid matrix of donor SOLs accommodated varying amounts of acceptor SOLs to tune the ground and excited state features. In all examples of donor-acceptor-based hybrid SOLs, even a low amount of acceptor, such as a donor-acceptor ratio of 1000:1, can cause pronounced optical properties. Hence, the evaluation of the optical properties of SOLs, especially, in the absence of solvents is so special that it avoids the interference of solvent molecules. Still, the major drawback of SOLs remains unsolved until we report polymerizable SOLs. Although a large variety of SOLs have been reported in the literature, the long-lasting problem of surface stickiness of SOLs was resolved by polymerizable SOLs. It enabled the development of flexible, foldable, and stretchable large-area luminescent films suitable for lighting and display devices. In this Account, we summarize our work on SOLs, hybrid SOLs, polymerizable SOLs, and the application of SOLs in selective sensing of explosives. Finally, an outlook on the feasibility of luminescent polymerizable SOLs in futuristic applications is provided.

}, issn = {0001-4842}, doi = {10.1021/acs.accounts.3c00670}, author = {Wakchaure, Vivek Chandrakant and Channareddy, Goudappagouda and Babu, Sukumaran Santhosh} }