Category Archives: research

Photophysics

Using photo physical tools our group we understand excited state processes to solve mechanistic puzzles, unravel new reactivity, develop new chemical paradigms from excited states and develop new systems that are responsive to light. Our group pursues  both steady state and time resolved techniques to address research challenges that originate from excited state reactivity.

1. Iyer, A; Clay, A. C.; Jockusch, S.; Sivaguru, J.*.Evaluating brominated thioxanthones as organo-photocatalysts. J. Phy. Org. Chem., 2017, 30:e3738. (Waldemar Adam Special Issue)
2. Wang, W; Clay, A; Krishnan, R; Lajkiewicz, N; Sivaguru, J;* Porco, J* Total Syntheses of the Aglain Natural Products Foveoglin A and Perviridisin B via selective ESIPT Photocycloaddition. Angew. Chem. Int. Ed., 2017,56, 14479 –14482.(accepted; DOI: 10.1002/anie.201707539 and 10.1002/ange.201707539). (Highlighted in Synfacts2018, 14, 0005).
3. Brown, S. L.; Krishnan, R.; Elbaradei, A.; Sivaguru, J.; Sibi, M. P.; Hobbie, E. K.“Origin of Stretched-Exponential Photoluminescence Relaxation in Size-Separated Silicon Nanocrystals,AIP Advances, 2017, 7, 55314.
4. Srinivasan, G.; Hoey, J.; Anderson, K.; Frohlich, M. T.; Krishnan, R.; Sivaguru, J.; Sibi, M. P. Boudjok. P. “Synthesis of Silicon Quantum Dots using Cyclohexasilane (Si6H12)” J. Mater. Chem. C, 2016, 4, 8206-8213.
5. Clay, A.; Vallavoju, N., Krishnan, R.; Ugrinov. A.; S., J. Sivaguru*Metal Free Visible Light Mediated Photocatalysis: Control-ling Intramolecular [2+2] Photocycloaddition of Enones through axial chirality. J. Org. Chem. 2016, 81, 7191−7200. (Special issue on Photocatalysis).
6. Vallavoju, N.; Sreenitya, A.; Ayitou, A.; Jockusch, S.; Sunoj, R. B.; and Sivaguru, J.* Photoreactions with a twist: Atropisomerism-driven divergent reactivity of enones with UV and visible light. Chem. E. J.2016, 22, 11339-11348.

Water remediation with Light

Photochemical/Photocatalytic approach to water remediation:

In collaboration with Prof. Eakalak Khan (Univ of Nevada, Las Vegas), a water resource engineer, we have developed photo-catalysts and photochemical methods to remove active pharmaceuticals, toxins (e.g. algal toxins) from water. To address the problem of chemicals that are prevalent in produced water after fracking (process used in oil and gas industries) that potentially contaminate fresh water sources (food-water nexus), we have developed a photocatalytic process to remove such contaminants utilizing visible light.

Photochemical removal of Toxins – References

1.  Martin, M. A.; Sivaguru, J.*; McEvoy, J.; Sonthiphand, P.; Delorme, A.; Khan, E. Photodegradation of (E)- and (Z)-Endoxifen in Water by Ultraviolet Light: Efficiency, Kinetics, By-Products, and Toxicity Assessment. Water Research, 2020, 171, 115451 (DOI: 1016/j.watres.2019.115451)

Photochemical removal of pollutants – References

2. Hong, S.; Ratpukdi, T.; Sivaguru, J.; Khan, E. A sustainable solution for removal of glutaraldehyde in saline water with visible light photocatalysis, Chemosphere, 2019, 220, 1083-1090. DOI: 10.1016/j.chemosphere.2018.12.21

3. Hong, S.; Ratpukdi, T.; Sivaguru, J.; Khan, E.Photolysis of glutaraldehyde in brine: A showcase study for removal of a common biocide in oil and gas produced water. Hazad. Mater. 2018, 353, 254-260

4. Sieverding, H. L.; Clay, D. E.; Khan, E.; Sivaguru, J.; Pattabiraman, M.; Koodali, R. T.; Ndiva-Mongoh, M.; Stone, J. J. A Sustainable Rural Food–Energy–Water Nexus Framework for the Northern Great Plains. Agric. Environ. Lett.2016, 1, 1-4.

Light responsive bio-mass derived polymers and coatings

Light initiated bio-mass derived polymers and coatings

Our group is also pursing photo responsive materials from biomass for developing high performance polymers and coatings.

1. Sivaguru, J. and Iyer, A.Hydrazide Based Molecular Templates For Applications In Material Chemistry, Synthesis And Biological Systems. (Patent filed on March 8, 2016; U.S. Patent Application No. 62/305,044.
2. Sivaguru, J.; Sibi, M. P.; Webster, D.; Singathi, R.; Raghunathan, R.; Krishnan, Rajendran, S.;  renewable and sustainable bio-mass derived photodegradable polymers. (Patent filed on April 18, 2016; Tech Id; Patent Serial No. 62/324,189).
3. Sivaguru, J.; Ulven, C.; Singati, R.; Ameri, A.;  Vanilin Based photodegradble composite materials. Provisional filed on Aug 23, 2017.

Bio-mass derived photo-initiators and photoacids

Bio-mass derived photo-initiators and photoacids

We have also developed new photo-initiators and photo-acids from biomass to showcase their utility to access high performance materials. In addition, they have superior photochemical and photophysical properties with an added advantage of minimizing our dependence on fossil fuels.

1. Clay, A.; Singathi, R.; Krishnan, R.; Jockusch, S.; Webster; D. Sibi, M. P.; Sivaguru, J. Photoacidity of Vanilin derivatives. Photochem. Photobiol. A. Chem.,2018,355, 38-41.
2. Sivaguru, J.; Sibi, M. P.; Webster, D.; Clay, A.; Raghunathan, R.; Singathi, R.; Krishnan, R.; Bio mass derived photoinitiators for the synthesis of a broad spectrum of polymers using uv and/or visible light. (Patent filed on April 18, 2016; Patent Serial No. 62/324194).

Programmed photodegradable and recyclable polymers from bio-resources

Photo-responsive degradable and recyclable materials from bio-resources, 

We developed a process to access polymeric materials from biomass that are programmed to degrade upon light exposure at a specific wavelength. These materials upon degradation regenerate the monomer allowing us the ability to recycle. The degradable aspect of the polymer can be fine-tuned at a specific wavelength depending on the end use of the materials. The research has impact beyond science as it addresses the problem of plastic pollution as well as our dependability on fossil fuels to access materials not to mention the added advantage of recyclability.

1. Saravanakumar, R.; Raghunathan, R; Krishnan, R.; Ugrinov, A.; Webster, D.; Sibi, M. P.; Sivaguru, J.* Programmed degradation of oligomeric/polymeric materials derived from renewable bio-resources. Chem., Int. Ed., 2015, 54, 1159-1163. (Back Cover article. highlighted in multiple media outlets both nationally and internationally).
2. Isola, C.; Sieverding, H. L.; Raghunathan, R.; Sibi, M. P.; Webster, D. C.; Sivaguru, J.; Stone, J. J. Life cycle assessment of photodegradable polymeric material derived from renewable bioresources Clean. Prod. 2017, 142, 2935-2944.
3. Sivaguru, J.; Sibi, M. P.; Webster, D. W.; Rajendran, S. K.; Raghunathan, R. Programmed Degradation of Polymers Derived from Biomass. U.S. Patent Application No. 14/883,798.

Photodegradation of Polymer

Organic Photochemistry

We have established the importance of restricted bond rotations in controlling excited state reactivity. Utilizing atropisomeric scaffolds we have unraveled new design features, with outcomes that are unique and unprecedented for excited state reactivity. For example, we have established that reactive spin states (singlet or triplet excited state) profoundly influence the stereochemical outcome of phototransformations. We have also detailed the use of low energy visible light rather than high energy UV light without compromising the stereoenrichment in the photoproducts. In general, the photochemistry and photophysics of atropisomeric substrates differ significantly from their achiral counterparts irrespective of having the same chromophore initiating the excited state reactivity. 
The generality and versatility of our strategy was detailed as an accounts of chemical research article signifying the scope of our strategy in accessing chirally enriched products during phototransformations. Some recent references related to our group’s contribution to organic and asymmetric photochemistry are below.

1. Kumarasamy, E; Ayitou, A. J. -L.; Vallavoju, N.; Raghunathan, R.; Iyer, A.; Clay, A.; Kandappa, S.; Sivaguru, J.*  Tale of Twisted Molecules: Taming Asymmetric phototransformations through non-biaryl atropisomers. Acc. Chem. Res. 2016. 49, 2713−2724.
2. Kumarasamy, E; Raghunathan, R.; Jockusch, S.; Sivaguru, J.* TransposedPaternò-BüchiReaction  J. Am. Chem. Soc., 2017, 139, 655–662.
3. Iyer, A; Jockusch, S.; Sivaguru, J.* Making the transition– Enablingtraditionalphotoreactionstoworkundervisiblelight. Chem. Commun. 2017, 53,1692-1695.
4. Kumarasamy, E.; Kandappa, S.; Raghunathan, R.; Jockusch, S.; Sivaguru, J.* RealizingAzaPaternò-Büchireaction” Angew. Chem.Int. Ed.2017, 56, 7056 –7061.(Frontispiece).

Supramolecular Photocatalysis

We have shown that one can utilize water soluble nano-containers as supramolecular catalysts to perform selective photochemical reactions. The supramolecular photocatalytic process displays features similar to an enzyme – reaction is allosteric with very minimal product inhibition with good turnover. More importantly, encapsulation of the reactant molecule within the nano-cavity protects the excited state enhancing reactivity. The reaction can be carried out in water with visible light showcasing utility as a green chemical process. Some representative publications/reviews on this topic from our group is below

1. Ramamurthy, V.; and Sivaguru. J.* “Supramolecular Photochemistry as a Potential Synthetic Tool” Chem. Rev. 2016, 116, 9914−9993.
2. Vallavoju, N.; Sivaguru, J.* Supramolecular Photocatalysis: Combining confinement and non-covalent interactions to control light initiated reactions. Soc. Rev., 2014, 43, 4084-4101.
3. Pemberton, B. C.; Kumarasamy, E.; Jockusch, S.; Srivatsava, D. K.; Sivaguru, J.* Photophysical aspects of 6-methylcoumarin-Cucurbit[8]uril Host-guest Complexes. J. Chem., 2011,89, 310-316.
4. Pemberton, B. C.; Barooah, N.; Srivatsava, D. K.; Sivaguru, J.* Supramolecular photocatalysis by confinement—photodimerization of coumarins within cucurbit[8]urils Commun. 2010, 46, 225-227. (Hot paper in Chem. Commun./synfacts highlight).

Supramolecular
Photocatalysis

Organo-photocatalysis

Results from our group has established the use of  stereoelectronic effects to manipulate excited state reactivity similar to ground state enantioselective transformations under organo-catalytic control. This opens up avenues to exploit the well-known stereoelectronic effects to control reactivity and selectivity for some of the most synthetically useful excited state transformations. Some of the recent publication from our group is listed below.

1. Vallavoju, N; Sermadurai, S.; Pemberton, B. C.; Jockusch, S.; Sibi, M. P.; Sivaguru, J.* Insights into the mechanistic aspects of organo-photocatalysis mediated by thioureas. Chem., Int. Ed. 2016, 55, 5446-5451.(Selected as “important paper” and featured as a frontispiece).
2. Kumarasamy, E.; Sibi, M. P.; Sivaguru, * Non-biaryl and hetero-biaryl atropisomers: Molecular templates with promise for atropselective chemical transformations”, Chem. Rev.,2015,115, 11239–11300.
3. Vallavoju, N; Sermadurai, S.; Jockusch, S.; Sibi, M. P.; Sivaguru, J.* Enantioselective organo-photocatalysis mediated by atropisomeric thiourea derivatives. Angew Chem., Int. Ed., 2014, 53, 5604-5608 and Chem. 2014, 126, 5710-5714.
4. Vallavoju, N. Sermadurai, S.; Jockusch, S.; Prabhakaran, M. T.; Sibi, M. P.; Sivaguru, J.* Evaluating thiourea architecture for intramolecular [2+2]-photocycloaddition of 4-alkenylcoumarins. Synt. Catal., 2014, 356, 2763-2768.