Sreejith Shankar

• PhD
• Senior Scientist at National Institute for Interdisciplinary Science and Technology

Aza‐fused aromatic π–conjugated networks are an important class of 2D graphitic analogs, which are generally constructed using aromatic precursors. Herein, the study describes a new synthetic approach and electrochemical properties of a self‐exfoliating benzotristriazine 2D network (BTTN) constructed using aliphatic precursors, under relatively mil...

Lower Critical Solution Temperature (LCST) of macromolecular systems is important in thermoresponsive smart window design. However, controlling the LCST behavior and sustaining the shelf‐life are challenging tasks. Herein, how photochemistry can be tweaked to design sustainable smart windows that allow controlled transmission of solar radiation is...

Personal protective equipment (PPE), especially face masks, has received much attention as a quick reaction to pandemic outbreaks to prevent infections caused by airborne microorganisms. Single-use masks are generally made of synthetic polymers such as polypropylene. Discarding the used masks causes serious environmental pollution. Incineration is...

Diels–Alder photocycloaddition, a well‐known textbook reaction, has not been explored in materials chemistry. Herein we describe how this classical photochemistry can be used to modulate the lower critical solution temperature (LCST) of a molecular π‐system, which can further be exploited for the controlled transmission of solar radiation for the m...

Volumetric capacitance is a more critical performance parameter for rechargeable power supply in lightweight and microelectronic devices as compared to gravimetric capacitance in larger devices. To this end, we report three electrochromic metallopolymer-based electrode materials containing Fe2+ as the coordinating metal ion with high volumetric cap...

Diels‐Alder photocycloaddition, a well‐known text book reaction, has not been explored in materials chemistry. Herein we describe how this classical photochemistry can be used to modulate the lower critical solution temperature (LCST) of a molecular π‐system, which can further be exploited for controlled transmission of solar radiation for indoor h...

The present invention relates to design and applications of a class of water-soluble small molecules represented by Formula 1. In aqueous solutions the said molecules exhibit lower critical solution temperature (LCST) phase transition near room temperature, imparting a temperature triggered molecules switching of transparency stages . Further, it d...

Designing surface-confined molecular systems capable of expressing changes in functional properties as a result of slight variations in chemical structure under the influence of an external stimulus is of contemporary interest. In this context, we have designed three tetraterpyridine ligands with variations in their core architecture (phenyl vs tet...

Temperature is often not considered as a precision stimulus for artificial chemical systems in contrast to the host–guest interactions related to many natural processes. Similarly, mimicking multi‐state volatile memory operations using a single molecular system with temperature as a precision stimulus is highly laborious. Here we demonstrate how a...

Thermochromic metal complexes of bipyridyl ligands and their gels were shown to have broad application in controlled light transmission windows and logic operations. Herein, temperature is used as a precision input for effecting reversible multi‐step changes in the optical properties of metal–organic complexes. Such systems form archetypical protot...

Coordination polymers and metal–organic frameworks have attracted immense attention across different fields of science as materials with numerous functional applications. Herein, we report the use of coordination polymers obtained from near-isostructural metal (Mn²⁺, Fe²⁺, and Co²⁺) bipyridine complexes as electrode materials in a symmetric superca...

The very concept of dye and pigment chemistry that was long known to the industrial world underwent a radical revision after the discovery and commercialization of dyes such as mauveine, indigo, and so on. Apart from their conventional role as coloring agents, organic dyes, and pigments have been identified as indispensable sources for high-end tec...

Controlled switching of the spin state of transition metal ions, particularly of FeII and FeIII, is a prerequisite to achieve selectivity, efficiency, and catalysis in a number of metalloenzymes. Here we report on an iron(III) porphyrin with a photochromic axial ligand which, upon irradiation with two different wavelengths reversibly switches its s...

We report here a unique and efficient methodology for the surface functionalization of closed-cage (fullerene-like-IF) nanoparticles and inorganic nanotubes (INT) composed of two-dimensional (2D) nanomaterials of transition-metal chalcogenides (MS2; M = W or Mo). The first step is the physical coverage of these robust inorganic materials with monod...

We report here a new methodology for the formation of free-standing nanotubes composed of individual gold nanoparticles crosslinked by coordination complexes or porphyrin molecules using WS2 nanotubes (INT-WS2) as a template. Our method consists of three steps: (i) the coverage of these robust inorganic materials with monodispersed and dense monola...

In this study we have used a tetrahedral oligopyridine and four different fluoroiodides to obtain 3D-nanoporous halogen-bonded co-crystals. Many of the halogen-bonded co-crystals reported to date are 1D chains or 2D sheet-like structures; these new co-crystals possess multiple channels of 300-800 ų volume per unit cell. The extended 3D channels ca...

In this study, we demonstrate a versatile approach towards the formation of electrochromic nanoscale assemblies on transparent-conductive oxides on both rigid and flexible substrates. Our method is based on alternatively spin-coated layers of well-defined metal polypyridyl complexes and a palladium (II) salt to form electrochemically addressable fi...

The immobilization of metal nanoparticles (NPs) with molecular control over their organization is challenging. Herein, we report the formation of molecularly cross-linked AuNP assemblies using a layer-by-layer approach. We observed four types of assemblies: 1) small aggregates of individual AuNPs, 2) large aggregates of individual AuNPs, 3) network...

We demonstrate how the distance over which electron transfer occurs through organic materials can be controlled and extended. Coating of conductive surfaces with nanoscale layers of redox-active metal complexes allows the electrochemical addressing of distant layers that are otherwise electrochemically silent. Our materials can pass electrons selec...

This combined experimental and computational study demonstrates how a metal center can drastically influence the reactivity of a coordinated ligand. We found that the consecutive formation of zerovalent bimetallic complexes proceeds by fast η2-C═C coordination of only one Pd(PEt3)2 moiety, which then significantly slows down the subsequent reaction...

We demonstrate high-performance electrochromic assemblies that exhibit a practical combination of low--voltage operation, efficient electrochromic switching, as well as long--term thermal and redox--stability (1.12 × 10^5 cycles). Our molecular assemblies can be integrated into a solid--state configuration. Furthermore, we also show how the molecul...

Despite the tremendous progress made in the design of supramolecular and inorganic materials, it still remains a great challenge to obtain uniform structures with designed size and shape. Metal-organic frameworks (MOFs) and infinite coordination polymers (ICPs) are examples of rapidly emerging materials with useful properties, yet limited morpholog...

Tubulysins are highly toxic tubulin-targeting agents with a narrow therapeutic window that are interesting for application in antibody-drug-conjugates (ADCs). For full control over drug-antibody-ratio (DAR) and the effect thereof on pharmacokinetics and tumor targeting a dual-labeling approach was developed, wherein the drug, tubulysin variants, an...

Enabling and understanding new methodologies to fabricate molecular assemblies driven by intermolecular interactions is fundamental in Chemistry. The controlled surface-confinement of these materials remains a challenge. In this paper we demonstrate for the first time, a solvent-free on-surface crystal-to-co-crystal conversion process driven by hal...

Tubulysins are potent anti-mitotic natural compounds and a scalable and efficient synthetic route for generation of its analogues has been developed and extended to the synthesis of diastereoisomers and N-terminal analogues of tubulysin-U. Structure–activity-relationship studies on these synthetic analogues reaffirmed the significance of native ste...

Tubulysins are cytotoxic natural products with promising anti-cancer properties, originally isolated from myxobacterial cultures. Structurally, tubulysins are tetrapeptides, incorporating three unusual (Mep, Tuv and Tup) and one proteinogenic amino acid (Ile). Here we describe the synthesis and structure-activity relationship studies of novel tubul...

Natural product analogue generation is important, providing tools for chemical biology, enabling structure activity relationship determination and insight into the way in which natural products interact with their target biomolecules. The generation of analogues is also often necessary in order to improve bioavailability and to fine tune compounds'...

Tubulysins are strongly cytotoxic natural tetrapeptides with potent antiproliferative, antimitotic, and antiangiogenic activities which might find use in oncology. We herein report the first total synthesis of a stereoisomerically pure oxazole analogue of tubulysin U, which was found to be more cytotoxic than the thiazole-containing natural product...

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Herein we report the highly asymmetric aza-Michael reactions of α,β-enones (2-enoylthiazoles) with metalated chiral oxazolidinones under different reaction conditions and for different substituents at the β-position of the Michael acceptor. The reaction proceeds with complete diastereoselectivity to give exclusively one of the two diastereomers. Th...