Breaking of Kasha's Rule: Excitation Wavelength-Dependent Emission from Acenaphthylene-Based Hydrazones and their Biological Studies Rakshantha Srithar, Jayashree Venkatesh, Jegadheeshwari Saravanan, Kesavan Muthu, Susnata Pramanik Chemphotochem, 2025 Achieving multicolor emissions from a single molecule has been an active field of research, particularly in developing organic light‐emitting diodes. Reported herein is acenaphthylenedione (AcD), which displays multiple colors as a function of excitation wavelengths. Experimental and theoretical data reveal that the latter emits strongly from S3 and weakly from S2, while S1 remains as a dark state, thus violating Kasha's rule. The calculated large energy difference between S2 and S3 (i.e., 1.00 eV) promotes radiative decay from S3 rather than internal conversion (IC) to S1. Hydrazones derived from the same also possess excitation wavelength‐dependent emission. Time‐dependent density functional theory (TDDFT) calculations reveal that the longer wavelength emission can be assigned to enol‐form, produced through excited‐state intramolecular proton transfer (ESIPT) and locally excited (LE) keto‐form, while that of the shorter wavelength to LE S2, thus disobeying Kasha's rule. The calculated energy difference (ΔES1‐S2) is found to be 0.64 eV, which reduces the rate of IC (i.e., S2 → S1), resulting in the emission from the higher excited state. N‐methylated hydrazone, which blocks the ESIPT channel, also supports the hypothesis. Furthermore, all the compounds exhibit aggregation‐induced emission behavior, and nitro‐ and cyano‐substituted hydrazones are found as good candidates for antibacterial, antioxidant, and anticancer activities.
A Mechanistic Insight into the Emission Behavior of Boron Difluorohydrazones (BODIHYs): Suppression of Kasha's Rule Rakshantha Srithar, Naveen Kumar M, Renitta Benny, Sudhakar Gaikwad, Soumen De, et al. Chemistry A European Journal, 2025 Abstract Single component‐based molecules and materials exhibiting excitation wavelength‐dependent emission are of significant interest in both academic and industrial contexts. Luminophores capable of emitting multiple colors in response to different excitation wavelengths often deviate from Kasha's rule. The boron difluorohydrazone ( BODIHY ) derivatives reported herein exhibit excitation wavelength‐dependent emissions, illuminating red, green, and blue (RGB) colors. Experimental and theoretical studies indicate that this multi‐color luminescence originates from three bright excited states, namely, S 1 , S 2 , and S 3 . Such anomalous fluorescence in small organic molecules that possess three bright excited states and emit RGB as a function of excitation wavelength is unique and unprecedented. Time‐dependent density functional theory (TDDFT) calculations indicate that the energy gap (ΔE) between S 2 and S 3 exceeds 3000 cm −1 (0.37 eV), facilitating radiative decay S 3 →S 0 over the competitive nonradiative decay. For compound 1 , the ΔE (S1–S2) was found to be < 2000 cm −1 (0.25 eV), leading to thermal equilibrium between the two states. In contrast, compound 2 possesses three distinct excited states that fluoresce independently due to large energy gaps between them. Furthermore, different excitation spectra, fluorescence lifetimes, and photoluminescence quantum yields (PLQYs) for these emission bands indeed support the presence of three bright excited electronic states.
(Supra)Molecular Switches Controlled by Artificial Signaling Cascades Soumen De, Susnata Pramanik, Michael Schmittel, Jayashree Venkatesh, Akanksha Sharma Synlett, 2025 Biological communication is an indispensable component of intra- and extracellular regulation of life. Inspired by such complicated control networks, systems chemistry has begun to advance tools for autonomous networks by developing communication protocols between molecular entities to up- and downregulate functions (simple catalysis, dual catalysis, time-encoded emission). However, up to now these protocols remain relatively simple, indicating that there will be a long way to self-sustaining and autonomous functional systems. This review focuses on communication in artificial multicomponent systems that operate under either equilibrium or dissipative conditions, detailing the design principles for their operations. Finally, we discuss the key differences between biological and artificial signaling, emphasizing the limitations of artificial signaling and suggesting future directions in the field of artificial signal transduction. 1 Introduction2 Communication and Information Processing in Artificial Systems: Toward Smart Systems Chemistry2.1 Type 1: External Signal with One Sender, One Messenger, and One Receiver2.2 Type 2: External Signal with One Sender, One Messenger, and Two Receivers2.3 Type 3: One/Two External Signal(s) with Two Senders, Two Messengers, and One/Two Receiver(s)2.4 Type 4: External Signal with Cascaded Communication Across Multiple Receivers2.5 Type 5: Signaling Cascade Leading to Multiple Chemical Reactions2.6 Type 6: Signaling Cascade with Self-Regulation3 The Bigger Picture4 Conclusion and Outlook
Controlling the Chiroptical Properties of Pyrene-Based Tweezers by Conformation Locking Renitta Benny, Nithish Kumar, Anshuman Bera, Rakshantha Srithar, Susnata Pramanik, Sivaranjana Reddy Vennapusa, Soumen De Chemphotochem, 2025 Circularly polarized excimer emission is highly sought‐after due to its potential in advanced optoelectronic and sensing applications. However, achieving precise control over this phenomenon remains a significant challenge. To address this challenge, we have designed a system where circularly polarized excimer emission could be controlled via conformation locking and aggregation. The structural conformations were extensively examined using circular dichroism spectroscopy, X‐ray crystallography, 1H NMR spectroscopy, and molecular modelling. Self‐assembly was triggered by adding water to THF solutions, with water‐induced aggregation leading to redshifts in absorption bands and excimer emission in T1 (major monomer emission), T2 (minor monomer emission) and T3 at high water content. Additionally, the effects of aggregation on chiroptical properties were studied using circular dichroism and circularly polarized luminescence spectroscopy, revealing a reduction in circular dichroism signal and circularly polarized luminescence quenching with increasing water content. Notably, T3 displayed both excimer and monomer circularly polarized luminescence signals, reflecting two excited‐state geometries. This research underscores the impact of rigidity on the photophysical and chiroptical properties of pyrene and opens avenues for further exploration of BINOL‐pyrene‐based macrocycles and cages.
Glucose biosensors Rakshantha Srithar, Naveen Kumar M., Susnata Pramanik Fundamentals of Biosensors in Healthcare Volume 1, 2024
Metal and Proton Relay-Controlled Hierarchical Multistep Switching Cascade Heyifei Fu, Susnata Pramanik, Ivan Aprahamian Journal of the American Chemical Society, 2023 Transition metals play an important role in many biological processes including cellular regulation and signal transduction. Emulating such processes on the molecular level, while challenging, can help us learn how to manipulate intermolecular communication, an important requirement for the development of solution-based molecular machines. In this work, we demonstrate a transition metal-based artificial multistep switching cascade that exhibits intrinsic hierarchical level control. The process starts with Zn(II), which initiates a transition metal relay by displacing a macrocycle-encapsulated Pd(II). The latter then binds to a hydrazone switch leading to coordination-coupled deprotonation (CCD). Finally, the proton generated through CCD activates the E/Z isomerization of a second noncoordinating pH-sensitive hydrazone switch. This whole multistep process can be reset to the original state by removing the Pd(II) from the system.
One system, three functions: an electroactive reconfigurable organic receptor for adaptive binding, information encoding, and metal-free oxidation L Seethapathy, R Muthusamy, CK Hazra, J Samanta, S Pramanik, R Das Materials Horizons , 2026 2026
A Mechanistic Insight into the Emission Behavior of Boron Difluorohydrazones (BODIHYs): Suppression of Kasha's Rule R Srithar, N Kumar M, R Benny, S Gaikwad, S De, S Pramanik Chemistry–A European Journal 31 (49), e02168 , 2025 2025 Citations: 1
Breaking of Kasha's Rule: Excitation Wavelength‐Dependent Emission from Acenaphthylene‐Based Hydrazones and their Biological Studies R Srithar, J Venkatesh, J Saravanan, K Muthu, S Pramanik ChemPhotoChem 9 (9), e202500137 , 2025 2025 Citations: 2
(Supra) Molecular Switches Controlled by Artificial Signaling Cascades J Venkatesh, A Sharma, S De, S Pramanik, M Schmittel Synlett , 2025 2025 Citations: 2
Controlling the Chiroptical Properties of Pyrene‐Based Tweezers by Conformation Locking R Benny, N Kumar, A Bera, R Srithar, S Pramanik, S Reddy Vennapusa, ... ChemPhotoChem 9 (5), e202400396 , 2025 2025 Citations: 4
Achieving white light emission from a hydrazone through three different channels: AIE, solvatochromism and excitation wavelength J Venkatesh, R Srithar, S Pramanik Chemical Communications 61 (78), 15254-15257 , 2025 2025 Citations: 1
Glucose biosensors R Srithar, N Kumar, S Pramanik Fundamentals of Biosensors in Healthcare, 405-433 , 2025 2025
Enhanced dual state emission from tri-and tetraphenylethene-substituted pyrene-fused heteroacenes R Ahamed, KS Godi, A Bhadke, S Fisher, RK Gamidi, S Pramanik, ... ChemRxiv 2024 (1001) , 2024 2024
Metal and proton relay-controlled hierarchical multistep switching cascade H Fu, S Pramanik, I Aprahamian Journal of the American Chemical Society 145 (36), 19554-19560 , 2023 2023 Citations: 13
Excitation wavelength-dependent multi-coloured and white-light emissive pyrene-based hydrazones: suppression of Kasha's rule N Kumar, DL Lyngkhoi, S Gaikwad, J Samanta, R Ahamed, S Khatua, ... Chemical Communications 59 (95), 14122-14125 , 2023 2023 Citations: 10
The effect of substituents on the aggregation-induced emission of 9, 10-phenanthraquinone-hydrazones N Kumar, DL Lyngkhoi, S Gaikwad, D Samanta, S Khatua, S Pramanik New Journal of Chemistry 47 (32), 15066-15075 , 2023 2023 Citations: 5
Carbohydrate recognition using metal–ligand assemblies R Ahamed, J Venkatesh, R Srithar, S Gaikwad, S Pramanik Organic & Biomolecular Chemistry 21 (27), 5492-5505 , 2023 2023 Citations: 7
Photochromic hydrazone switches I Abrahamian, H Qian, S PRAMANIK, B SHAO, Q Li US Patent 11,279,677 , 2022 2022 Citations: 2
Hydrazone photoswitches for structural modulation of short peptides M Jeong, J Park, Y Seo, K Lee, S Pramanik, S Ahn, S Kwon Chemistry–A European Journal 28 (11), e202103972 , 2022 2022 Citations: 19
Light-mediated chiroptical switching of an achiral foldamer host in presence of a carbohydrate guest S Pramanik, B Kauffmann, S Hecht, Y Ferrand, I Huc Chemical Communications 57 (1), 93-96 , 2021 2021 Citations: 23
Remote control of the reversible assembly/disassembly of supramolecular aggregates N Mittal, I Paul, S Pramanik, M Schmittel Supramolecular Chemistry 32 (2), 133-138 , 2020 2020 Citations: 6
Three-state switching in a double-pole change-over nanoswitch controlled by redox-dependent self-sorting S Gaikwad, MS Özer, S Pramanik, M Schmittel Organic & Biomolecular Chemistry 17 (34), 7956-7963 , 2019 2019 Citations: 8
Catalytically active nanorotor reversibly self-assembled by chemical signaling within an eight-component network A Goswami, S Pramanik, M Schmittel Chemical Communications 54 (32), 3955-3958 , 2018 2018 Citations: 25
A high-speed network of nanoswitches for on/off control of catalysis S Gaikwad, S Pramanik, S De, M Schmittel Dalton Transactions 47 (6), 1786-1790 , 2018 2018 Citations: 18
Photochromic hydrazone switches with extremely long thermal half-lives H Qian, S Pramanik, I Aprahamian Journal of the American Chemical Society 139 (27), 9140-9143 , 2017 2017 Citations: 220
MOST CITED SCHOLAR PUBLICATIONS
Photochromic hydrazone switches with extremely long thermal half-lives H Qian, S Pramanik, I Aprahamian Journal of the American Chemical Society 139 (27), 9140-9143 , 2017 2017 Citations: 220
Orthogonality in discrete self-assembly–survey of current concepts ML Saha, S De, S Pramanik, M Schmittel Chemical Society Reviews 42 (16), 6860-6909 , 2013 2013 Citations: 208
Reversible ON/OFF nanoswitch for organocatalysis: mimicking the locking and unlocking operation of CaMKII. M Schmittel, S De, S Pramanik Angewandte Chemie (International ed. in English) 51 (16), 3832-3836 , 2012 2012 Citations: 132
Hydrazone switch-based negative feedback loop S Pramanik, I Aprahamian Journal of the American Chemical Society 138 (46), 15142-15145 , 2016 2016 Citations: 98
A toggle nanoswitch alternately controlling two catalytic reactions S De, S Pramanik, M Schmittel Angewandte Chemie International Edition 53 (51), 14255-14259 , 2014 2014 Citations: 89
Networking nanoswitches for ON/OFF control of catalysis N Mittal, S Pramanik, I Paul, S De, M Schmittel Journal of the American Chemical Society 139 (12), 4270-4273 , 2017 2017 Citations: 71
A reversible nanoswitch as an ON–OFF photocatalyst M Schmittel, S Pramanik, S De Chemical Communications 48 (96), 11730-11732 , 2012 2012 Citations: 67
Bidirectional chemical communication between nanomechanical switches S Pramanik, S De, M Schmittel Angewandte Chemie International Edition 53 (18), 4709-4713 , 2014 2014 Citations: 64
Spontaneous and catalytic fusion of supramolecules ML Saha, S Pramanik, M Schmittel Chemical Communications 48 (76), 9459-9461 , 2012 2012 Citations: 57
A monomer–dimer nanoswitch that mimics the working principle of the SARS-CoV 3CLpro enzyme controls copper-catalysed cyclopropanation S De, S Pramanik, M Schmittel Dalton Transactions 43 (28), 10977-10982 , 2014 2014 Citations: 38
A trio of nanoswitches in redox-potential controlled communication S Pramanik, S De, M Schmittel Chemical Communications 50 (87), 13254-13257 , 2014 2014 Citations: 37
Catalytically active nanorotor reversibly self-assembled by chemical signaling within an eight-component network A Goswami, S Pramanik, M Schmittel Chemical Communications 54 (32), 3955-3958 , 2018 2018 Citations: 25
Light-mediated chiroptical switching of an achiral foldamer host in presence of a carbohydrate guest S Pramanik, B Kauffmann, S Hecht, Y Ferrand, I Huc Chemical Communications 57 (1), 93-96 , 2021 2021 Citations: 23
Hydrazone photoswitches for structural modulation of short peptides M Jeong, J Park, Y Seo, K Lee, S Pramanik, S Ahn, S Kwon Chemistry–A European Journal 28 (11), e202103972 , 2022 2022 Citations: 19
A high-speed network of nanoswitches for on/off control of catalysis S Gaikwad, S Pramanik, S De, M Schmittel Dalton Transactions 47 (6), 1786-1790 , 2018 2018 Citations: 18
Metal and proton relay-controlled hierarchical multistep switching cascade H Fu, S Pramanik, I Aprahamian Journal of the American Chemical Society 145 (36), 19554-19560 , 2023 2023 Citations: 13
Redox-dependent self-sorting toggles a rotary nanoswitch M Schmittel, S De, S Pramanik Organic & Biomolecular Chemistry 13 (33), 8937-8944 , 2015 2015 Citations: 12
Dual coordination in ditopic azabipyridines and azaterpyridines as a key for reversible switching S De, S Pramanik, M Schmittel Dalton Transactions 42 (43), 15391-15398 , 2013 2013 Citations: 12
Excitation wavelength-dependent multi-coloured and white-light emissive pyrene-based hydrazones: suppression of Kasha's rule N Kumar, DL Lyngkhoi, S Gaikwad, J Samanta, R Ahamed, S Khatua, ... Chemical Communications 59 (95), 14122-14125 , 2023 2023 Citations: 10
Three-state switching in a double-pole change-over nanoswitch controlled by redox-dependent self-sorting S Gaikwad, MS Özer, S Pramanik, M Schmittel Organic & Biomolecular Chemistry 17 (34), 7956-7963 , 2019 2019 Citations: 8
