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146 results on '"Grover, Nitika"'

9. On-Surface Synthesis of Polyphenylene Wires Comprising Rigid Aliphatic Bicyclo[1.1.1]Pentane Isolator Units

Author

Yang, Biao, Niu, Kaifeng, Cao, Nan, Grover, Nitika, Zhao, Wenchao, Riss, Alexander, Björk, Jonas, Auwaerter, Willi, Barth, Johannes V., Senge, Mathias O., Yang, Biao, Niu, Kaifeng, Cao, Nan, Grover, Nitika, Zhao, Wenchao, Riss, Alexander, Björk, Jonas, Auwaerter, Willi, Barth, Johannes V., and Senge, Mathias O.

Abstract

Bicyclo[1.1.1]pentane (BCP) motifs are of growing importance to the pharmaceutical industry as sp(3)-rich bioisosteres of benzene rings and as molecular building blocks in materials science. Herein we explore the behavior of 1,3-disubstituted BCP moieties on metal surfaces by combining low-temperature scanning tunneling microscopy / non-contact atomic force microscopy studies with density functional theory modeling. We examine the configuration of individual BCP-containing precursors on Au(111), their supramolecular assembly and thermally activated dehalogenative coupling reactions, affording polymeric chains with incorporated electronically isolating units. Our studies not only provide the first sub-molecular insights of the BCP scaffold behavior on surfaces, but also extend the potential application of BCP derivatives towards integration in custom-designed surface architectures., Funding Agencies|Technical University of Munich-Institute for Advanced Study through a Hans Fischer Senior Fellowship; Science Foundation Ireland (SFI) [21/FFP-A/9469]; Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) [453903355]; Swedish research council; Bavarian state ministry for education, science, and the arts visiting professor program; Projekt DEAL

Published
2023
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33. An Insight into Non‐Covalent Interactions on the Bicyclo[1.1.1]pentane Scaffold.

Author

Grover, Nitika, Flanagan, Keith J., Trujillo, Cristina, Kingsbury, Christopher J., and Senge, Mathias O.

Subjects
*PENTANE, *DRUG interactions, *FUNCTIONAL groups, *MONOMERS
Abstract

Bicyclo[1.1.1]pentane (BCP) is studied extensively as a bioisosteric component of drugs. Not found in nature, this molecular unit approximates the distance of a para‐disubstituted benzene which is replaced in medicines as a method of improving treatments. Predicting interactions of these drugs with specific active sites requires knowledge of the non‐covalent interactions engaged by this subunit. Structure determinations and computational analysis (Hirshfeld analysis, 2D fingerprint plots, DFT) of seven BCP derivatives chosen to probe specific and directional interactions. X‐ray analysis revealed the presence of various non‐covalent interactions including I ⋅⋅⋅ I, I ⋅⋅⋅ N, N−H ⋅⋅⋅ O, C−H ⋅⋅⋅ O, and H−C ⋅⋅⋅ H−C contacts. The preference of halogen bonding (I ⋅⋅⋅ I or I ⋅⋅⋅ N) in BCP 1–4 strictly depends upon the electronic nature and angle between bridgehead substituents. The transannular distance in co‐crystals 2 and 4 was longer as compared to monomers 1 and 3. Stronger N−H ⋅⋅⋅ O and weaker C−H ⋅⋅⋅ O contacts were observed for BCP 5 while the O ⋅⋅⋅ H interaction was a prominent contact for BCP 6. The presence of 3D BCP units prevented the π ⋅⋅⋅ π stacking between phenyl rings in 3, 4, and 7. The BCP skeleton was often rotationally averaged, indicating fewer interactions compared to bridgehead functional groups. Using DFT analysis, geometries were optimized and molecular electrostatic potentials were calculated on the BCP surfaces. These interaction profiles may be useful for designing BCP analogs of drugs. [ABSTRACT FROM AUTHOR]

Published
2021
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35. Synthetic Advances in the C–H Activation of Rigid Scaffold Molecules.

Author

Grover, Nitika and Senge, Mathias O.

Subjects
*ADAMANTANE, *PENTANE, *FUNCTIONAL groups, *MOLECULES
Abstract

The remarkable structural and electronic properties of rigid non-conjugated hydrocarbons afford attractive opportunities to design molecular building blocks for both medicinal and material applications. The bridgehead positions provide the possibility to append diverse functional groups at specific angles and in specific orientations. The current review summarizes the synthetic development in CH functionalization of three rigid scaffolds namely: (a) cubane, (b) bicyclo[1.1.1]pentane (BCP), (c) adamantane. 1 Introduction 2 Cubane 2.1 Cubane Synthesis 2.2 Cubane Functionalization 3 Bicyclo[1.1.1]pentane (BCP) 3.1 BCP Synthesis 3.2 BCP Functionalization 4 Adamantane 4.1 Adamantane Synthesis 4.2 Adamantane Functionalization 5 Conclusions and Outlook [ABSTRACT FROM AUTHOR]

Published
2020
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36. N‐Confused Porphyrin – A Unique "Turn‐On" Chemosensor for CN− and F− ions and "Turn‐Off" Sensor for ClO4− ions.

Author

Grover, Nitika and Sankar, Muniappan

Subjects
*PORPHYRINS, *DIPYRROMETHANES, *FLUORESCENCE quenching, *IONS, *BINDING constant, *REDUCTION potential, *FLUORESCENCE
Abstract

N‐Confused meso‐tetrakis(4‐carbomethoxyphenyl)porphyrin (1) and its Ni(II) complex (1 a) have been synthesized and utilized for anion sensing studies, and the results are compared with N‐confused meso‐tetraphenylporphyrin (NCTPP). Anion susceptibilities of 1 and 1 a were investigated using spectroscopic, electrochemical, and DFT studies. Porphyrins 1 and 1 a were able to detect CN−, F−, and ClO4− ions selectively over the tested set of anions even at ppm level. Interestingly, the addition of ClO4− ions resulted in fluorescence quenching (turn off) whereas the addition of F− or CN− resulted in fluorescence enhancement (turn on). Notably, the TFA addition resulted in fluorescence quenching, whereas the fluorescence enhancement was observed while adding TBAOH. The higher association constant (Ka) values with anions, lower detection limit, and shifts in redox potentials are due to the electron‐withdrawing effect of the −COOCH3 group at the para‐position of the meso‐phenyl ring. This electron‐withdrawing nature is crucial for the higher affinity towards anions. The anion sensing description in this article may not only unveil the built‐in nature of N‐confused porphyrins, but may also provide a general proposal for the development of novel anion sensors based on porphyrinoids. The electron‐deficient porphyrin framework, large polarisable π‐system, and anion binding through the outer NH or a combination of the above factors serve as a foundation for N‐confused porphyrin to act as an anion sensor. [ABSTRACT FROM AUTHOR]

Published
2020
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43. Investigation of the Reactivity of 1-Azido-3-iodobicyclo[1.1.1]pentane under “Click” Reaction Conditions

Author

Sitte, Elisabeth, Twamley, Brendan, Grover, Nitika, and Senge, Mathias O.

Abstract

The bicyclo[1.1.1]pentane (BCP) unit is under scrutiny as a bioisostere in drug molecules. We employed methodologies for the synthesis of different BCP triazole building blocks from one precursor, 1-azido-3-iodobicyclo[1.1.1]pentane, by “click” reactions and integrated cycloaddition–Sonogashira coupling reactions. Thereby, we accessed 1,4-disubstituted triazoles, 5-iodo-1,4,5-trisubstituted triazoles, and 5-alkynylated 1,4,5-trisubstituted triazoles. This gives entry to the synthesis of multiply substituted BCP triazoles on either a modular or a one-pot basis. These methodologies were further utilized for appending porphyrin moieties onto the BCP core.

Published
2021
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46. Versatile Synthetic Route for β-Functionalized Chlorins and Porphyrins by Varying the Size of Michael Donors: Syntheses, Photophysical, and Electrochemical Redox Properties

Author

Chaudhri, Nivedita, Grover, Nitika, and Sankar, Muniappan

Abstract

One-pot facile synthesis and characterization of novel β-substituted meso-tetraphenylporphyrins and/or chlorins were described. The high regioselective reactivity of active methylene compounds in Michael addition reaction was reported to access β-substituted trans-chlorins. Size-dependent approach was applied for the fine-tuning of product formation from porphyrins to chlorins. Notably, we were able to isolate mono/trisubstituted porphyrin and/or di/tetra-substituted chlorin from one-pot synthesis for the first time in porphyrin chemistry. Single-crystal X-ray diffraction analysis revealed the quasiplanar to moderate nonplanar conformation of chlorins due to transorientation of β-substituents, whereas porphyrins exhibited higher mean plane deviation from 24-atom core (Δ24) as compared to chlorins. β-Functionalized chlorins exhibited lower protonation constants and much higher deprotonation constants as compared to porphyrins revealing the combined effect of the conformation of macrocyclic core and the electronic nature of β-substituents. Facile synthesis of porphyrins and/or chlorins based on the size of Michael donor employed and in turn resulted in tunable photophysical and electrochemical redox properties are the significant features of the present work.

Published
2024
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47. 1O2Mediated Conversion of β-Enaminonitriles to α-Keto Amides Photosensitized by Recyclable H2TPP in Visible Light

Author

Kumar, Rohit, Grover, Nitika, and Jain, Nidhi

Abstract

We report a one-step approach for the conversion of β-enaminonitriles to synthetically versatile α-keto amides in moderate to high yields under visible light irradiation photosensitized by porphyrins. The method is mild, cost-effective, and sustainable and requires air as the sole reagent/oxidant. The reaction is believed to proceed via an ene-type pathway initiated by 1O2, followed by dehydration, imine hydrolysis, and subsequent nucleophilic substitution of the cyanide group by amine. The method offers a broad substrate scope and has also been extended for synthesis of α-keto esters with aliphatic alcohols as nucleophiles. The porphyrin recovered after the reaction can be reused multiple times.

Published
2024
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