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Dive into the research topics where Vellanki Lakshmi is active.

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Featured researches published by Vellanki Lakshmi.


Journal of Organic Chemistry | 2011

Synthesis of sterically crowded polyarylated boron-dipyrromethenes.

Vellanki Lakshmi; Mangalampalli Ravikanth

A rapid synthetic route for polyarylated boron-dipyrromethenes using hexabromo boron-dipyrromethene as the key synthon is described. The X-ray structure revealed that the polyarylated BODIPY adopts a propeller-like conformation. These compounds exhibit red-shifted absorption and fluorescence bands with decent quantum yields and reversible oxidation and reduction waves when compared to unsubstituted boron-dipyrromethenes.


Journal of Organic Chemistry | 2013

Synthesis of Conjugated BODIPYs via the Wittig Reaction

Vellanki Lakshmi; Mangalampalli Ravikanth

A Wittig reaction was employed to synthesize conjugated BODIPYs in high yields by treating formylated BODIPYs with alkyl/aryl ylides under simple room temperature conditions. Treatment of 3,5-diformyl BODIPYs or α-formyl 3-pyrrolyl BODIPY with different alkyl/aryl ylides in CH2Cl2 at room temperature for 2 h followed by straightforward column chromatographic purification on silica afforded conjugated BODIPYs in ~65-90% yields. This is an alternate method to Knoevenagel and Heck reactions which have been used to synthesize such conjugated BODIPYs. The method works very efficiently, and we prepared 12 substituted BODIPYs including cholesterol-substituted BODIPYs to demonstrate the versatility of the reaction. The spectral, electrochemical, and fluorescence properties of these conjugated BODIPYs are also described.


RSC Advances | 2013

Functionalized 3-pyrrolyl boron-dipyrromethenes

Tejinder Kaur; Vellanki Lakshmi; Mangalampalli Ravikanth

A series of mono-functionalized 3-pyrrolyl boron-dipyrromethenes containing functional groups such as bromo, formyl, cyano, nitro and trimethylsilylacetylene groups at the α-position of the uncoordinated pyrrole group were synthesized. Further to show the use of functionalized 3-pyrrolyl BODIPY, we treated α-bromo BODIPY with four different boronic acids such as phenyl, biphenyl, phenylacetyl and thienyl boronic acids under mild Pd(0) coupling conditions to afford α-aryl substituted 3-pyrrolyl BODIPYs. α-Dipyrromethanyl substituted 3-pyrrolyl BODIPY was synthesized by treating α-formyl 3-pyrrolyl BODIPY with pyrrole in the presence of TFA in CHCl3. The 3-pyrrolyl BODIPY appended with BODIPY (BODIPY dyad) at the α-position of uncoordinated pyrrole was synthesized by oxidizing 3-dipyrromethanyl BODIPY with DDQ followed by complexation with BF3·Et2O. All compounds were characterized by HRMS mass, NMR, absorption, electrochemical and fluorescence techniques. The spectral studies indicated that the presence of substituent at the α-position of uncoordinated pyrrole of 3-pyrrolyl BODIPY alter the electronic properties of the BODIPY core. The photophysical studies on BODIPY dyad indicated a possibility of energy transfer from the appended BODIPY unit to the 3-pyrrolyl BODIPY unit in BODIPY dyad.


Journal of Materials Chemistry C | 2014

Boron-dipyrromethene based multi-anionic sensor and a specific cationic sensor for Fe3+

Vellanki Lakshmi; Mangalampalli Ravikanth

Symmetrical and unsymmetrical phenylhydrazone substituted boron-dipyrromethenes were synthesized by treating 3,5-diformyl boron-dipyrromethene with phenylhydrazine/2,4-dinitrophenylhydrazine in ethanol at reflux temperature. The X-ray structure of the unsymmetrical boron-dipyrromethene (BODIPY) was shown to have an almost extended planar orientation of BODIPY with 2,4-dinitrophenylhydrozone unit at the 3-position and ethyl acetal at the 5-position with small torsional angles. A strong absorption band at ∼600 to 700 nm and a weak emission band at ∼620 to 710 nm were observed for the phenylhydrazone substituted BODIPYs. The compounds showed interesting absorption properties in DMSO and DMF solvents compared to other solvents by shifting ∼150 nm towards the red region. Anion binding studies indicated that the unsymmetrical phenylhydrazone substituted BODIPY could be applied as a sensor for F−, CH3COO− and H2PO4− ions as confirmed by various spectroscopic studies. Furthermore, the unsymmetrical phenylhydrazone substituted BODIPY had the unique ability of acting as a two step fluorescence enhanced chemodosimetric sensor for Fe3+ ion.


New Journal of Chemistry | 2016

Effects of five membered aromatic heterocycles at the meso-position on the electronic properties of 3-pyrrolyl BODIPY

Ritambhara Sharma; Vellanki Lakshmi; Tamal Chatterjee; Mangalampalli Ravikanth

The first examples of 3-pyrrolyl boron dipyrromethenes (3-pyrrolyl BODIPY) containing five membered aromatic heterocycles such as pyrrole, thiophene and furan in place of a six membered aryl group at the meso-position were synthesized under simple reaction conditions. The presence of a five membered aromatic heterocycle in place of a six membered aryl group at the meso-position significantly alters the electronic properties of 3-pyrrolyl BODIPY as reflected in their spectral, photophysical and electrochemical properties. The X-ray structure solved for meso-furyl 3-pyrrolyl BODIPY showed that the appended pyrrole is more deviated from the mean plane of the BODIPY core compared to meso-aryl 3-pyrrolyl BODIPY. However, the structure also revealed that the meso-furyl group is more in plane with the BODIPY core and participates in π-delocalization unlike meso-aryl 3-pyrrolyl BODIPY in which the meso-aryl group is almost in perpendicular orientation with the BODIPY core. The absorption studies indicated that the meso-heterocyclic 3-pyrrolyl BODIPYs showed bathochromic shifts with maximum shifts noted for meso-furyl 3-pyrrolyl BODIPY compared to meso-aryl BODIPY. The meso-heterocyclic 3-pyrrolyl BODIPYs were weakly fluorescent and stable under electrochemical reduction conditions.


RSC Advances | 2014

Polyarylated boron-dipyrromethenes containing three different types of aryl groups

Vellanki Lakshmi; Mangalampalli Ravikanth

We report the synthesis and properties of the first examples of four novel multiply hexaarylated boron-dipyrromethenes (BODIPYs) containing three different types of aryl groups on each pyrrole ring of BODIPY. The BODIPYs were synthesized over a sequence of steps of bromination followed by Suzuki coupling with arylboronic acids. All reactions worked smoothly and we isolated the multiply polyarylated BODIPYs as stable fluorescent solids in high yields. The hexaarylated BODIPYs and associated reference compounds were confirmed by HR-MS and characterized by NMR, absorption, fluorescence and electrochemical techniques. The multiply polyarylated BODIPYs absorb strongly in the 550–600 nm region and emit in the 590–640 nm region with decent quantum yields and singlet state lifetimes. The polyarylated BODIPYs are very stable under redox conditions.


Reports in Organic Chemistry | 2016

Functionalized boron-dipyrromethenes and their applications

Vellanki Lakshmi; Ritambhara Sharma; Mangalampalli Ravikanth

License. The full terms of the License are available at http://creativecommons.org/licenses/by-nc/3.0/. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. Permissions beyond the scope of the License are administered by Dove Medical Press Limited. Information on how to request permission may be found at: http://www.dovepress.com/permissions.php Reports in Organic Chemistry 2016:6 1–24 Reports in Organic Chemistry Dovepress


Organic and Biomolecular Chemistry | 2015

Halogenated boron-dipyrromethenes: synthesis, properties and applications.

Vellanki Lakshmi; Malakalapalli Rajeswara Rao; Mangalampalli Ravikanth


Journal of Physical Chemistry C | 2015

Vectorial Charge Separation and Selective Triplet-State Formation during Charge Recombination in a Pyrrolyl-Bridged BODIPY–Fullerene Dyad

Venugopal Bandi; Habtom B. Gobeze; Vellanki Lakshmi; Mangalampalli Ravikanth; Francis D’Souza


Dalton Transactions | 2012

Brominated boron dipyrrins: synthesis, structure, spectral and electrochemical properties

Vellanki Lakshmi; Mangalampalli Ravikanth

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Mangalampalli Ravikanth

Indian Institute of Technology Bombay

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Ritambhara Sharma

Indian Institute of Technology Bombay

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Tamal Chatterjee

Indian Institute of Technology Bombay

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G. Santosh

Indian Institute of Technology Bombay

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Tejinder Kaur

Indian Institute of Technology Bombay

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Yogita Pareek

Indian Institute of Technology Bombay

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Way Zen Lee

National Taiwan Normal University

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Venugopal Bandi

University of North Texas

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