Browsing by Author "Shukla, Tarun"

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Acid/Base and H2PO4- Controllable High-Contrast Optical Molecular Switches with a Novel BODIPY Functionalized [2]Rotaxane
(2015-12-09)
Arumugaperumal, Reguram
;
Srinivasadesikan, Venkatesan
;
Raju, Mandapati V. Ramakrishnam
;
Lin, Ming-Chang
;
Shukla, Tarun
A novel multifunctional mechanically interlocked switchable [2]rotaxane R4 containing two molecular stations and rotaxane arms terminated with boron-dipyrromethene (BODIPY) fluorophores and its derivatives were synthesized for the first time by CuAAC click reaction. The shuttling motion of macrocyde between the dibenzylammonium and triazolium recognition sites and the distance dependent photoinduced electron transfer process of R4 is demonstrated by utilizing external chemical stimuli (acid/base). Interestingly, the reversible self-assembly process of R4 was recognized by the acid-base molecular switch strategy. Notably, two symmetrical triazolium groups acted as molecular stations, H2PO4- receptors, and H-bonded donors. Both [2]rotaxane R4 and thread R2 demonstrated excellent optical responses and high selectivity toward H2PO4- ion. The specific motion and guest-host interactions of mechanically interlocked machines (MIMs) were also further explored by quantum mechanical calculations. The thread R2 also demonstrated to enable the detection of H2PO4- in RAW 264.7 cells successfully.
Facile rhodamine-based colorimetric sensors for sequential detections of Cu(II) ions and pyrophosphate (P2O74-) anions
(2016-01-01)
Arumugaperumal, Reguram
;
Srinivasadesikan, Venkatesan
;
Lin, Ming-Chang
;
Shellaiah, Muthaiah
;
Shukla, Tarun
Two rhodamine hydrazine derivatives Rh1 and Rh2 with catechol and ether functionalities have been synthesized and utilized towards sequential colorimetric detections of Cu(II) and pyrophosphate (PPi) ions in CH3CN-H2O (v/v = 9 : 1, 5 mM Tris-HCl, pH 7.4) semi-aqueous medium. Notably, Rh1 and Rh2 are the first example of colorimetric rhodamine-based probes for the sequential detections of Cu2+ ion and PPi anion. Based on the significant colorimetric responses (from colorless to pink) of Rh1 and Rh2 to Cu2+ ions, the detection limits were estimated as low as 1.22 x 10(-8) M and 8.0 x 10(-7) M, respectively, which signified the utilities of designed probes towards facile detections of Cu2+ ions. Furthermore, upon the successive addition of PPi ion to Rh1-Cu2+ and Rh2-Cu2+ complexes, it has been altered and restored to its origin of Rh1 and Rh2 via re-coordination of PPi to Cu2+ ion, which was confirmed by color changes from pink to colorless. Moreover, computational DFT calculations provided more insights into HOMO-LUMO structures of rhodamine derivatives and their copper complexes. Additionally, the solid state strip-based colorimetric detections of Cu2+ ion were supplemented as a real time application.
Multi-stimuli-responsive high contrast fluorescence molecular controls with a far-red emitting BODIPY-based [2]rotaxane
(2018-10-01)
Arumugaperumal, Reguram
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Venkatesan, Parthiban
;
Shukla, Tarun
;
Raghunath, Putikam
;
Singh, Ravinder
A novel fluorescent switchable [2]rotaxane NIR4 composed of two different molecular stations and rotaxane arms terminated with far-red boron-dipyrromethene (BODIPY) fluorophores and its derivatives were synthesized by CuAAC click chemistry. The molecular shuttling motion of mechanically interlocked molecules (MIMs) could be addressed by the fluorescence signal transduction via distance dependent photo-induced electron transfer process of [2]rotaxane NIR4 triggered by external chemical stimuli of acid/base. Moreover, the flexible arms of triazolium moiety in [2]rotaxane NIR4 and its axle NIR2 exhibited impressive selectivity and sensitivity toward complementary anionic analyte (H2PO4-), where the specific mechanical molecular motion was supported by quantum mechanical calculations. The development of [2]rotaxane NIR4 with a high level of structural complexity can be utilized for novel dual sensory detections of acid-base and dihydrogen phosphate (H2PO4-) anion. Importantly, the host of NIR2 and [2]rotaxane NIR4 could be applied for the vitro imaging and clarify the distribution of H2PO4- at subcellular levels.
Novel supramolecular conjugated polyrotaxane as an acid-base controllable optical molecular switch
(2017-05-01)
Shukla, Tarun
;
Arumugaperumal, Reguram
;
Raghunath, Putikam
;
Lin, Ming-Chang
;
Lin, Chien-Min
To study the supramolecular interactions of the mechanically interlocked rotaxane pendants with the backbone of two comparable conjugated polymers, axle polymer P1 and polyrotaxane P2 were synthesized by copolymerization of fluorine-based monomer F with phenanthroimidazole (PIZ)-based axle monomer A and rotaxane monomer R, respectively. Prevailing H-1 NMR, UV-vis and PL profiles revealed that polyrotaxane P2 showed sensitive and reversible acid-base molecular switching properties via supramolecular interactions in contrast to the other analogous polymer P1. The capability of molecular switching is also proven by computational study. Apparently, the controllable nano self-assembly process of P2 was fulfilled by reversible acid-base molecular switch approaches, where the orthogonal H-bonded polyrotaxane units were converted from bloated form into flake form on protonation. (C) 2016 Elsevier B.V. All rights reserved.