Author Image

Hi, I am Mukunda!

Mukunda Mandal

Postdoctoral researcher at The University of Chicago

My research focuses primarily on quantum chemical calculations and in silico screenings of potential catalysts and functional materials to address real-world issues such as sustainability and energy. Specific research directions include understanding polymerization reaction mechanisms, catalysis utilizing heterogeneous support materials like metal-organic frameworks, C–H functionalization reactions relevant to pharmaceuticals and agrochemicals, as well as metal-halide perovskite materials for solar cells and lighting.

Professional Positions

UChicago Logo
The University of Chicago
Postdoctoral Research Associate
Advisor: Prof. Laura Gagliardi
Research Interests:
  • Application of multireference-based methods in catalysis
  • Enzyme-mimicking catalysis by MOFs
Apr 2023 – Present
Chicago, IL
MPI-P Mainz Logo
Max Planck Institute for Polymer Research
Humboldt Postdoctoral Fellow
Group Leader: Dr. Denis Andrienko
Research Interests:
  • Metal-halide perovskite nanocrystals
  • 2D organic/inorganic hybrid perovskites
  • Nanographene/graphene heterostructures
Sep 2020 – Apr 2023
Mainz, RP, Germany
CSIR NCL Logo
CSIR-National Chemical Laboratory
Research Intern
Advisor: Prof. Debashree Ghosh
Research Project:
  • Computed ionization potentials of building-blocks of eumelanin to estimate its ionization threshold
Jan 2015 – Jun 2015
Pune, India

Education

IIT Bombay Logo
Indian Institute of Technology (IIT) Bombay
MSc in Chemistry
Advisor: Prof. G. Naresh Patwari

Master's Thesis: Study of Phenylacetylene Analogues in the Gas Phase using Time of Flight Mass Spectrometry

2012 – 2014
Mumbai, India
RKMRC Narendrapur Logo
2009 – 2012
Narendrapur, WB, India

Research Interests

Polymers

Project-01 Description

Plastic pollution is a major environmental concern that requires immediate action. One potential solution is to replace petroleum-based plastics with biodegradable or compostable polymers made from biomass-derived monomers. Bioplastics can be synthesized using ring-opening polymerization (ROP), which often requires the use of metal alkoxide catalysts to facilitate the reaction. Our research aims to better understand the mechanisms of ROP and identify ways to optimize the process through the development of faster and more efficient catalysts, with the ultimate goal of making bioplastics more commercially viable.

Perovskites

Project-02 Description

Metal-halide perovskites (MHPs) are a class of materials that have gained significant attention due to their exceptional performance in a variety of applications, including solar cells and light-emitting diodes (LEDs). These materials have a general formula of ABX3, where X is an anion that is bonded to both A+ and B2+ cations. Our research involves the study of both bulk perovskite materials and perovskite nanocrystals (PNCs). Our focus is on improving the efficiency of exciton generation in bulk perovskite materials for use in solar cells, and eliminating carrier recombination pathways. Additionally, we are interested in enhancing charge transport between PNCs through the use of virtual screening to identify ligands with extended π-conjugation that can replace the native insulating ligands on the PNCs.

Proton-Coupled Electron Transfer

Project-03 Description

Small-molecule mononuclear copper(III) compounds, such as hydroxo, peroxo, and benzoate, which mimic biological molecules/enzymes, have been found to initiate hydrocarbon oxidation by activating X–H bonds (X = C, O). These reactions can occur through hydrogen-atom transfer (HAT) or concerted proton-coupling electron transfer (cPCET). In our research, we utilize theoretical techniques such as the analysis of the total dipole moment vector oriented along the hydrogen donor-acceptor axis and direct visualization of the localized intrinsic bond orbitals as they evolve along the reaction coordinate to distinguish between HAT and cPCET mechanisms.

Metal–Organic Frameworks

Project-04 Description

Due to their crystalline structure and porosity, Metal–organic frameworks (MOFs) are an appealing choice as support materials for catalytic moieties. To demonstrate this, our synthesis team synthesized two single-site heterogeneous catalysts by immobilizing vanadium oxide (VOx) species on zirconium- and hafnium-based MOFs, Zr-NU-1000 and Hf-MOF-808, respectively. We then used a DFT-based approach to study the structural features of these VOx-incorporated MOFs, or V-MOFs, and probed their reactivity towards selective oxidation of benzyl alcohol to benzaldehyde. Additionally, the structure and reactivity of palladium-based catalysts anchored to acid-functionalized hafnium-based MOFs were examined, and it was found that the acid-functionalized MOF nodes enhanced catalytic activity.

Benzylic C–H Functionalization

Project-05 Description

In this collaborative project, copper-catalyzed radical relay chemistry is used to functionalize diverse molecules with benzylic C–H bonds under mild conditions, resulting in the formation of C–X bonds (X = CN, N3, OMe). The mechanism and enantioselectivity of this reaction are of significant interest to organic synthesis and in particular to medicinal and agricultural chemistry. Using density functional theory, we analyzed multiple potential energy surfaces to understand C–X bond formation. Our results indicate that the mechanism of the reaction depends on the nucleophile X, leading to enantioselectivity in certain cases (X = CN) but not in others (X = N3, OMe).

Melanin

Project-06 Description

Melanin is a pigment found in human skin that can both protect against and contribute to photodamage. Although photodegradation of melanin has been linked to photoionization processes, little is known about the oxidation potential of melanin and its monomers. In this project, we calculated the ionization energies of eumelanin monomers, dimers, and oligomers to determine the threshold energy for ionization, which we found to be within the UV-B range. Additionally, we examined the charge and spin distributions of ionized monomers to understand which ionization channels might promote eumelanin monomerization.

Nanographene

Project-07 Description

This research focuses on the use of hybrid nanographene–graphene (NG–Gr) van der Waals heterostructures (vdWHs) as materials for optoelectronic devices. We found that adjusting the size of synthesized NGs can control the strength of van der Waals interactions in NG–Gr vdWHs, which enables control over interfacial charge transfer. The interfacial charge transfer efficiency and rate in NG-Gr vdWHs increased when the size of NGs were increased from 42 to 96 sp2 carbon atoms, despite the reduction in the interfacial energy driving the charge transfer process. These findings suggest that vdW interactions are the primary factor in determining the interfacial charge transfer efficiency in NG–Gr vdWHs, while interfacial energetics and reorganization energy have only a minor influence.

Temperature Sensor

Project-08 Description

This research aims to develop a molecular probe that can be used to measure temperature in vivo during magnetic resonance imaging (MRI). We used virtual screening to identify organofluorine compounds that could potentially improve the accuracy and sensitivity of 19F MRI-based temperature monitoring. In collaboration with our experimental team, we have developed a perfluoro-sulfane-based compound that showed a nearly 2-fold increase in temperature responsiveness compared to the current standard 19F MRI temperature sensor (perfluoro-tributylamine) and the 1H resonance frequency, a standard parameter used for temperature mapping in MRI. The ultimate goal of this work is to enhance the diagnostic capabilities of 19F MRI and promote the use of fluorine magnetic resonance techniques in clinical practice.

All Publications

Jun 24, 2024
Odd-Even Alkyl Chain Effects on the Structure and Charge Carrier Transport of Two-Dimensional Sn-based Perovskite Semiconductors
J. Am. Chem. Soc. 2024, (In Press).

Synopsis: A distinct odd-even oscillation of the charge carrier transport in 2D Sn-based perovskite semiconductors by incorporating phenylalkylammonium-based organic cations with different alkyl side chain lengths with odd and even carbon atoms is observed.

JACS 2024 TOC

Key Takeaways:

  • Odd vs. even alkyl chain effect on the structure and charge transport properties of 2D Sn-based perovskites is explored.
  • Odd carbon chains result in disordered crystal lattices and larger electron/hole effective mass, leading to lower mobilities.
  • Even carbon chains leads to planar, ordered [SnI6]-octahedra layers, and hence improved mobilities.

December 8, 2023
Mechanistic Insights into Radical Formation and Functionalization in Copper/N-Fluorobenzenesulfonimide Radical-Relay Reactions
Chem. Sci. 2024, 15, 1364.

Synopsis: Cu-catalyzed C(sp3)–H functionalization with NFSI utilizes the Cu-bound •NSI radical for selective benzylic C–H bond activation, with the resulting radical functionalization pathways dependent on the copper-bound nucleophile.

Chem. Sci. 2024 TOC

Key Takeaways:

  • In Cu-catalyzed C(sp3)–H functionalization with NFSI, the Cu-bound •NSI radical is the active HAT reagent and selectively activates benzylic C–H bonds over 3° C–H bonds (superior vs. other HAT reagents like •OtBu and •Cl).
  • The radical functionalization pathway depends on the Cu-bound nucleophile, with options including radical-polar crossover, reductive elimination from a CuIII organometallic complex, and radical addition to a Cu-bound ligand.
  • Comparing 3 routes for transforming benzylic C–H bonds into their respective cations revealed that HAT/ET (relevant to Cu/NFSI chemistry) provides a wider substrate scope than hydride transfer (relevant in high-potential quinones) and sequential ET/PT/ET (employed in photoredox catalysis).

Jun 23, 2022

Key Takeaways:

  • In perovskite-silicon tandem solar cells, the presence of C60 molecules at the interface with the perovskite layer can create shallow trap states and lead to high levels of interface recombination, reducing the power conversion efficiency (PCE) of the cells.
  • Addition of an ultrathin metal-fluoride interlayer at the perovskite/C60 interface can reduce nonradiative recombination and improve electron extraction, resulting in a higher PCE of 29.3%.
  • Insertion of an interlayer can also address the issue of a surface dipole at the pristine perovskite/C60 interface, which can hinder electron extraction.
  • (MgF2)n layers serve as a better “electron sink” than (LiF)n layers, enabling more efficient charge extraction.

Aug 09, 2022

Key Takeaways:

  • Large hysteresis and poor field-effect behavior associated with severe ion migration can render perovskite field-effect transistors (FET) unreliable.
  • The hot-casting method can be used to control grain size and grain boundary density in perovskite films to improve charge carrier transport.
  • Hot-cast Sn(II)-based 2D perovskite FETs containing thiophene-based organic cation spacer TEA showed moderate increases in local hole mobility and significant FET performance improvements.

June 28, 2022
Improvement of Photophysical Properties of CsPbBr3 and Mn2+:CsPb(Br,Cl)3 Perovskite Nanocrystals by Sr2+ Doping for White Light-Emitting Diodes
J. Phys. Chem. C 2022, 126, 11277.

Synopsis: Addition of a small amount of Sr2+ dopant to pristine CsPbBr3 and Mn2+-doped CsPb(Br,Cl)3 perovskite nanocrystals improves the photoluminescence quantum yields and luminous efficiency of white LEDs by reducing defect density.

JPC C 2022 TOC

Key Takeaways:

  • Optoelectronic properties of metal halide perovskite nanocrystals (PNCs) with the formula ABX3 are studied through the effect of B-site doping with Sr2+ ions on pristine CsPbBr3 and Mn2+-doped Mn2+:CsPb(Br,Cl)3 PNCs.
  • ~2% Sr2+ doping improved the photoluminescence quantum yields of CsPbBr3 and Mn2+:CsPb(Br,Cl)3 PNCs and increased the luminous efficiency of white LEDs constructed with Sr2+-doped PNCs by approximately 4.7% compared to undoped PNCs.
  • Improved performance of Sr2+-doped PNCs is attributed to reduced defect density and attenuated microstrain in the local PNC structure, suggesting that adding a small amount of Sr2+ dopant to pristine perovskite materials can be a successful strategy for improving the optical properties of PNCs.

June 13, 2022
Quantum Efficiency Enhancement of Lead-Halide Perovskite Nanocrystal LEDs by Organic Lithium Salt Treatment
ACS Appl. Mater. Interfaces 2022, 14, 28985.

Synopsis: Treatment of perovskite nanocrystals (PNCs) with p-dopant LiTFSI, an organic lithium salt, improves optoelectronic properties such as photoluminescence quantum yields, exciton lifetimes, and external quantum efficiencies in PNCs and LEDs derived from them.

ACS AMI 2022 TOC

Key Takeaways:

  • Surface defect passivation is important for improving optoelectronic properties of lead halide perovskite nanocrystals (LHP NCs).
  • Treatment with p-dopant LiTFSI, an organic lithium salt, has multiple benefits for LHP NCs and LEDs derived from them, including higher photoluminescence quantum yields, longer exciton lifetimes, and higher external quantum efficiencies.
  • Density functional modeling shows that TFSI ligands change the surface dipole moment of slabs, leading to a significant shift in the vacuum level, while also preventing the harmful reduction of Pb2+ to Pb0 on the surface.

February 22, 2022
Development of a Highly Responsive Organofluorine Temperature Sensor for 19F Magnetic Resonance Applications
Anal. Chem. 2022, 94, 3782.

Synopsis: A perfluoro-sulfane-based compound is developed as a molecular probe for in vivo temperature monitoring during magnetic resonance imaging, showing a nearly 2-fold increase in temperature responsiveness compared to the current standard.

Anal. Chem. 2022 TOC

Key Takeaways:

  • A molecular probe is developed that can measure temperature in vivo during magnetic resonance imaging (MRI).
  • Virtual screening was used to identify organofluorine compounds that could potentially improve the accuracy and sensitivity of 19F MRI-based temperature monitoring.
  • A perfluoro-sulfane-based compound showed a nearly 2-fold increase in temperature responsiveness compared to perfluoro-tributylamine, the current standard 19F MRI temperature sensor.

February 15, 2022
Tuning Interfacial Charge Transfer in Atomically Precise Nanographene-Graphene Heterostructures by Engineering van der Waals Interactions
J. Chem. Phys. 2022, 156, 074702.

Synopsis: The strength of van der Waals interactions in hybrid nanographene-graphene heterostructures can be controlled by adjusting the size of synthesized nanographenes, with larger nanographenes resulting in increased charge transfer efficiency and rate.

JCP 2022 TOC

Key Takeaways:

  • Hybrid nanographene-graphene van der Waals heterostructures are studied for optoelectronic device applications.
  • Adjusting the size of synthesized nanographenes controls the strength of van der Waals interactions and interfacial charge transfer in these structures.
  • Interfacial charge transfer efficiency and rate increase with nanographene size, despite a reduction in driving interfacial energy. Van der Waals interactions dominate interfacial charge transfer efficiency in these structures, while interfacial energetics and reorganization energy have a minor impact.

February 16, 2022

Key Takeaways:

  • The presence of surface defects and their effect on the fluorescence properties of supercrystals of self-assembled CsPbX3 (X = Cl, Br) perovskite nanocrystals (PNCs) are investigated.
  • At the edges of the supercrystal, a fluorescence blueshift and decreased fluorescence lifetimes are observed due to a loss of structural coherence, atomic misalignment, and compressive strain.
  • Minimizing strain during the self-assembly of PNCs into supercrystals is important for lighting applications such as superfluorescent emitters.

December 19, 2021
Porphyrin Functionalization of CsPbBrI2/SiO2 Core-Shell Nanocrystals Enhances the Stability and Efficiency in Electroluminescent Devices
Adv. Optical Mater. 2022, 10, 2101945.

Synopsis: Native surface ligands on all-inorganic CsPbBrI2/SiOx perovskite nanocrystals were replaced with exciton delocalizing mono-functionalized porphyrin derivatives, resulting in increased phase stability and improved optoelectronic properties.

Adv. Optical Mater. 2021 TOC

Key Takeaways:

  • Native surface ligands (oleic acid/oleylamine) on all-inorganic CsPbBrI2/SiOx perovskite nanocrystals (PNCs) were replaced with exciton delocalizing mono-functionalized porphyrin derivatives, mMTPP (M = Zn, Mg, H2).
  • Electronic interaction between the mMTPP ligand and the inorganic PNC core is evidenced by the dislocation of the “electron” state (LUMO) onto the ligand, which lowers the first excitonic transition energy and contributes to lowering the charging energy.
  • The ligand-exchanged PNCs showed increased phase stability and improved optoelectronic properties and were used in an LED with higher current efficacy and improved charge carrier balance.

August 6, 2020
Structure and Reactivity of Single-Site Vanadium Catalysts Supported on Metal-Organic Frameworks
ACS Catal. 2020, 10, 10051.

Synopsis: Two vanadium oxide catalysts attached to two different MOFs were studied using DFT, revealing that the MOF node architecture significantly affected their catalytic activity toward selective oxidation of benzyl alcohol to benzaldehyde.

ACS Catal. 2020 TOC

Key Takeaways:

  • Two single-site heterogeneous catalysts were synthesized by immobilizing vanadium oxide (VOx) species on two MOFs, Zr-NU-1000 and Hf-MOF-808.
  • The structure and reactivity of these VOx-incorporated MOFs, or V-MOFs, towards selective oxidation of benzyl alcohol to benzaldehyde was explored using density functional theory.
  • Turnover-limiting C–H activation during benzyl alcohol oxidation was found to involve a concerted proton-coupling electron transfer mechanism.
  • Aside from the metal in the node, the MOF node architecture significantly affected the catalytic activity of the two V-MOFs.

June 15, 2020
Site-Selective Copper-Catalyzed Azidation of Benzylic C–H Bonds
J. Am. Chem. Soc. 2020, 142, 11388.

Synopsis: A radical-polar crossover pathway for benzylic azidation with a CuII-azide species and a benzyl radical coupling partner is presented, showing unique site-selectivity and producing benzyl azides that can be converted to different functional groups.

JACS 2020 TOC

Key Takeaways:

  • A copper-catalyzed method for benzylic C–H azidation is presented.
  • Experimental and density functional studies suggest that the reaction proceeds through a radical-polar crossover pathway involving a CuII-azide species and a benzyl radical.
  • The method exhibits unique site-selectivity compared to other C–H azidation methods and produces benzyl azides that can be converted into a variety of functional groups, including amines, triazoles, tetrazoles, and pyrroles, for use in target molecule synthesis and medicinal chemistry.

February 24, 2020
Copper-Catalyzed Benzylic C–H Coupling with Alcohols via Radical Relay Enabled by Redox Buffering
Nat. Catal. 2020, 3, 358.

Synopsis: A copper-catalyzed oxidative cross-coupling reaction was developed to synthesize diverse benzyl ethers by coupling benzylic C–H bonds with alcohols, using dialkylphosphites as in situ reductants which allowed for the regeneration of catalytically active CuI.

Nat. Catal. 2020 TOC

Key Takeaways:

  • A copper-catalyzed oxidative cross-coupling reaction was developed to synthesize diverse benzyl ethers by coupling benzylic C–H bonds (limiting reagent) with alcohols.
  • Typical reaction conditions resulted in the accumulation of inactive CuII, but the use of dialkylphosphites, (MeO)2P(O)H, as in situ reductants allowed for the regeneration of catalytically active CuI.
  • This redox buffering strategy may not be specific to this type of reaction and could potentially be used to discover and develop other radical relay C(sp3)–H cross-coupling methods that have a broad range of applications in medicinal chemistry and organic synthesis.

February 18, 2020
Mechanism of Stereocontrol in Polymerization of rac-Lactide by Aluminum Complexes Supported by Indolide-Imine Ligands
Macromolecules 2020, 53, 1809.

Synopsis: Aluminum complexes supported by salen-like indolide-imine ligands were found to catalyze stereoselective polymerization of rac-lactide, and it was concluded that the stereochemistry of initiation in these complexes is governed thermodynamically, not kinetically.

Macromolecules 2020 TOC

Key Takeaways:

  • L2AlOBn and L7AlOBn complexes (Bn = benzyl) supported by an analog of salen ligand incorporating indolide arms connected via their 2- and 7-positions, were found to catalyze stereoselective polymerization of rac-lactide to isotactically enriched polylactide.
  • NMR spectroscopy, X-ray crystal structures, and density functional theory were used to study the initiation reactions and examine the stereocontrol.
  • The stereochemistry of initiation in these complexes is governed thermodynamically, not kinetically.

November 11, 2019
Carboxylate Structural Effects on the Properties and Proton-Coupled Electron Transfer Reactivity of [CuO2CR]2+ Cores
Inorg. Chem. 2019, 58, 15872.

Synopsis: CuIII-carboxylate complexes with varying –R groups revealed a correlation between their redox properties, UV-vis characteristics, and PCET rates and suggested an oxidatively asynchronous PCET mechanism sensitive to the oxidative power of [CuIII(O2CR)]2+.

IC 2019 TOC

Key Takeaways:

  • Copper(II) carboxylate complexes [LCuII(O2CR)] with varying R-groups were studied, most with N,N′,N″-coordination by the supporting ligand.
  • Redox properties, UV-vis ligand-to-metal charge transfer features, and rates of hydrogen atom abstraction from 2,4,6,-tri-tbutylphenol using oxidized LCuIII(O2CR) complexes correlated with the electron donating nature of R.
  • The results support an oxidatively asynchronous proton-coupled electron transfer mechanism that is sensitive to the oxidative power of the [CuIII(O2CR)]2+ core.

October 16, 2019
Mechanisms for Hydrogen-Atom Abstraction by Mononuclear Copper(III) Cores: Hydrogen-Atom Transfer or Concerted Proton-Coupled Electron Transfer?
J. Am. Chem. Soc. 2019, 141, 17236.

Synopsis: The reactivity of LCuIII–Y complexes (Y = OH, OOCm, O2CAr) in activating X–H bonds (X = C, O) varies based on differing oxidizing abilities of the CuIII complexes and X–H bond functionalization mechanisms, with LCuIII–OH showing the highest reactivity.

JACS 2019 TOC

Key Takeaways:

  • Formally copper(III)–oxygen complexes LCuIII–OH (1), LCuIII–OOCm (2) and LCuIII–O2CAr (3) can activate X–H bonds (X = C, O).
  • Complex 1 reacts the fastest with O–H or C–H based substrates, followed by 3, followed by unreactive 2.
  • The reactivity of 13 varies due to differing oxidizing abilities and X–H bond functionalization mechanisms, which can be either hydrogen-atom transfer (HAT) or concerted proton-coupling electron transfer (cPCET) and vary based on the substrate and copper functionality.

April 29, 2019
Enhanced Activity of Heterogeneous Pd(II) Catalysts on Acid Functionalized Metal-Organic Frameworks
ACS Catal. 2019, 9, 5383.

Synopsis: Acid functionalization of the MOF node with PO42– and SO42– groups stabilizes PdII site in MOF-supported PdII catalysts and enhances their catalytic activity in the oxidative Heck reaction by preventing catalyst deactivation due to Pd0 aggregation.

ACS Catal 2019 TOC

Key Takeaways:

  • The structure and electronic properties of palladium single-site heterogeneous catalysts in phosphated and sulfated MOFs are studied.
  • The PO42– and SO42– groups in the MOFs stabilize the Pd(II) site and enhance catalytic activity in the oxidative Heck reaction.
  • Density functional calculations suggest that acid functionalization of the MOF node can stabilize the Pd(0) intermediate state during the reaction and prevent catalyst deactivation due to Pd(0) aggregation.

March 5, 2019
Architectural Control of Isosorbide-Based Polyethers via Ring-Opening Polymerization
J. Am. Chem. Soc. 2019, 141, 5107.

Synopsis: The annulation and subsequent conversion of rigid sugar-derived monomer, isosorbide, into linear or cyclic polymers via cationic and quasi-zwitterionic ring-opening polymerization are discussed, revealing its potential for use in high-performance materials.

JACS 2019 TOC

Key Takeaways:

  • Isosorbide is a rigid, sugar-derived monomer that has potential in high-performance materials.
  • Controlled polymerization methods for isosorbide have been lacking.
  • This study provides insights into the cationic and quasi-zwitterionic ring-opening polymerization of an annulated isosorbide derivative, allowing for the formation of either linear or cyclic polymers.

December 31, 2018
Computational Prediction and Experimental Verification of ϵ-Caprolactone Ring-Opening Polymerization Activity by an Aluminum Complex of an Indolide/Schiff-Base Ligand
ACS Catal. 2019, 9, 885.

Synopsis: An efficient {N,N,N,N}-aluminum complex with a bis-indolide Schiff-base ligand for the ring-opening polymerization of ε-caprolactone was identified through computational screening, synthesis, characterization and experimental reactivity evaluation.

ACS Catal 2018 TOC

Key Takeaways:

  • Computational screening was performed to identify aluminum complexes with high activity in ring-opening polymerization (ROP) of ϵ-caprolactone.
  • An {N,N,N,N}-aluminum complex with a bis-indolide Schiff-base ligand was predicted to be efficient.
  • Prediction was tested and verified through synthesis and characterization of the complex and evaluation of its ROP reactivity.

February 27, 2018
Sterically Induced Ligand Framework Distortion Effects on Catalytic Cyclic Ester Polymerizations
Inorg. Chem. 2018, 57, 3451.

Synopsis: The effectiveness of aluminum salen catalysts with o-adamantyl and o-tbutyl substituents in initiating the polymerization of ε-caprolactone is compared, revealing that bulky o-substituents improve the reactivity by distorting the precatalyst geometry in a favorable way.

IC 2018 TOC

Key Takeaways:

  • Effectiveness of aluminum salen complexes with o-adamantyl substituents in initiating the polymerization of ε-caprolactone was compared to that of similar salen catalysts having o-tbutyl substituents.
  • DFT modeling indicates that the reactivity of the catalyst is influenced by both the length of the backbone linker and the presence of o-aryl substituents on the ligand.
  • Bulky o-substituents distorts the pre-catalyst geometry in a favorable way, making it easier to achieve the rate-limiting TS geometry, thus speeding up the reaction.

November 8, 2017
Mechanism of the Polymerization of rac-Lactide by Fast Zinc Alkoxide Catalysts
Inorg. Chem. 2017, 56, 14366.

Synopsis: The rate of polymerization of rac-lactide using LXZn catalysts was found to be less sensitive to electronic effects of ligand substituents. Changing phenol para-substitutions changed Zn partial charge only slightly, suggesting that extensive nitrogen functionality around Zn buffers the effect of phenol substitution.

IC 2017 TOC

Key Takeaways:

  • Polymerization of rac-lactide (rac-LA) using LXZn catalysts was studied using kinetic experiments and DFT calculations.
  • LXZn catalysts were effective and relatively selective in polymerizing rac-LA with low dispersities, but the rate of polymerization was less affected by the electronic effects of ligand substituents (controlled by the para substituent X on the bound phenolate donor of the ligand) compared to earlier studies using aluminum catalysts.
  • DFT calculations provided insights into the mechanisms of initiation and propagation, helping to explain the high isotacticity and the insensitivity of the rate to the identity of the ligand substituent X.

October 6, 2017
Mechanistic Insights into the Alternating Copolymerization of Epoxides and Cyclic Anhydrides Using a (Salph)AlCl and Iminium Salt Catalytic System
J. Am. Chem. Soc. 2017, 139, 15222.

Synopsis: Epoxide/anhydride copolymerization using (salph)AlCl/[PPN]Cl catalytic pairs showed a first-order rate of polymerization for epoxide and zero-order for cyclic anhydride. The reaction proceeds via two catalytic cycles that share a common intermediate with carboxylate ligation, preventing possible side reactions.

JACS 2017 TOC

Key Takeaways:

  • Mechanistic studies of the copolymerization of 1-butene oxide and carbic anhydride using a (salph)AlCl/[PPN]Cl catalytic pair showed a first-order dependence of the polymerization rate on the epoxide and zero-order dependence on the cyclic anhydride.
  • Model complexes showed that a mixed alkoxide/carboxylate aluminum intermediate preferentially opens cyclic anhydride over epoxide, and ring-opening of epoxide by an intermediate comprising multiple carboxylates was rate-determining.
  • A mechanism involving two catalytic cycles is proposed where the copolymerization proceeds via intermediates with carboxylate ligation in common, avoiding a secondary cycle involving a bis-alkoxide species and explaining the lack of side reactions until the polymerization is complete.

December 22, 2016
Why So Slow? Mechanistic Insights from Studies of a Poor Catalyst for Polymerization of ε-Caprolactone
Inorg. Chem. 2017, 56, 725.

Synopsis: The rigidity of the ligand geometry of TMTAA(Al–OR) impairs its catalytic efficiency for the ring-opening polymerization (ROP) of ε-caprolactone, as a high energy input is required to induce deformation of the precatalyst geometry and reach the transition-state. This highlights the significance of ligand flexibility in the design of ROP catalysts.

IC 2017 TOC

Key Takeaways:

  • The polymerization of ε-caprolactone (CL) using an aluminum alkoxide catalyst (Al-TMTAA) was found to have a slower rate compared to other aluminum complexes.
  • DFT calculations showed that the ligand framework of the catalyst made trans binding of CL difficult, suggesting a concerted coordination–insertion for polymerization.
  • The sluggish performance of the catalyst is attributed to a high-framework distortion energy required to deform the ligand geometry, suggesting a need for ligand flexibility in the design of efficient polymerization catalysts.

October 6, 2015
Feasibility of Ionization-Mediated Pathway for Ultraviolet-Induced Melanin Damage
J. Phys. Chem. B 2015, 119, 13288.

Synopsis: The threshold energy for ionization of melanin monomers, dimers, and oligomers has been studied and found to fall within the UV-B range. The charge and spin distributions of ionized monomers were also studied to see which ionization channels promote monomerization.

JPC B 2015 TOC

Key Takeaways:

  • Melanin is a pigment found in human skin that can both protect against and contribute to photodamage.
  • The ionization energies of melanin monomers, dimers, and oligomers were calculated to determine the threshold energy for ionization, which was found to be in the UV-B range.
  • The charge and spin distributions of ionized monomers were examined to understand which ionization channels might promote melanin monomerization.