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Meelua W, Linnolahti M, Jitonnom J. Mechanism of cationic ring-opening polymerisation of ε-caprolactone using metallocene/borate catalytic systems: a DFT and NCI study on chain initiation, propagation and termination. RSC Adv 2024; 14:11715-11727. [PMID: 38605894 PMCID: PMC11008195 DOI: 10.1039/d4ra01178c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2024] [Accepted: 04/01/2024] [Indexed: 04/13/2024] Open
Abstract
We present a comprehensive DFT investigation on the cationic ring-opening polymerisation (CROP) of ε-caprolactone (CL) using zirconocene/borate catalyst systems. All possible pathways of the interaction between cationic species [Cp2ZrMe+] and counteranions, [A-] = [MeB(C6F5)3]- and [B(C6F5)4]-, were examined during chain initiation, propagation, and termination steps. The calculations reveal an active chain-end mechanism with O-alkyl bond cleavage of the polymerisation. The catalytic performance of the two counteranions is found to be identical, and they influence the initial process through stabilisation of the cationic species via non-covalent interactions (NCI), with the [MeB(C6F5)3]- anion stabilising the catalyst-monomer complex more effectively than the [B(C6F5)4]- anion by 24.3 kJ mol-1. The first two propagations are likely the rate-determining step, with calculated free-energy barriers of 61.4-71.2 and 73.9-80.6 kJ mol-1 with and without the anions (A-), respectively. The presence of the counteranion significantly affects the third propagation rate, lowering the barriers up to 20 kJ mol-1. Comparison of the first termination and the third propagation shows that they are not competitive, with the termination being less facile. We also studied the initiation and propagation steps for the hafnocene catalyst and found that the Hf catalyst slightly favours the CL CROP in comparison to the Zr catalyst. Analysis of solvent and dispersion interaction demonstrates that both factors play an important role in the process. NCI analysis reveals weak (van der Waals) interactions at the contacts between the cationic species and the counteranions during the reaction course. Overall, our results offer insights into the structures and interactions involved in the polymerisation.
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Affiliation(s)
- Wijitra Meelua
- Demonstration School, University of Phayao Phayao 56000 Thailand
- Unit of Excellence in Computational Molecular Science and Catalysis, and Division of Chemistry, School of Science, University of Phayao Phayao 56000 Thailand
| | - Mikko Linnolahti
- Department of Chemistry, University of Eastern Finland Joensuu Campus Yliopistokatu 7 FI-80100 Joensuu Finland
| | - Jitrayut Jitonnom
- Unit of Excellence in Computational Molecular Science and Catalysis, and Division of Chemistry, School of Science, University of Phayao Phayao 56000 Thailand
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Ganta PK, Teja MR, Chang CJ, Sambandam A, Kamaraj R, Chu YT, Ding S, Chen HY, Chen HY. Improvement of catalytic activity of aluminum complexes for the ring-opening polymerization of ε-caprolactone: aluminum thioamidate and thioureidate systems. Dalton Trans 2023; 52:17132-17147. [PMID: 37929915 DOI: 10.1039/d3dt03198e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2023]
Abstract
In this study, a series of Al complexes bearing amidates, thioamidates, ureidates, and thioureidates were synthesized and their catalytic activity for ε-caprolactone (CL) polymerization was evaluated. SPr-Al exhibited a higher catalytic activity than OPr-Al (3.2 times as high for CL polymerization; [CL] : [SPr-Al] : [BnOH] = 100 : 0.5 : 2; [SPr-Al] = 10 mM, conv. = 93% after 14 min at 25 °C), and USCl-Al exhibited a higher catalytic activity than UCl-Al (4.6 times as high for CL polymerization; [CL] : [USCl-Al] : [BnOH] = 100 : 0.5 : 2; [USCl-Al] = 10 mM, conv. = 90% after 15 min at 25 °C). Regardless of whether aluminum amidates or ureidates were present, thioligands improved the polymerization rate of aluminum catalysts. Density functional theory calculations revealed that the eight-membered ring [SPr-AlOMe2]2 decomposed into the four-membered ring SPr-AlOMe2. However, [OPr-AlOMe2]2 did not decompose because of its strong bridging Al-O bond. The overall activation energy required for CL polymerization was lower when using [SPr-AlOMe2]2 (18.1 kcal mol-1) as a catalyst than when using [OPr-AlOMe2]2 (23.9 kcal mol-1). This is because the TS2a transition state of SPr-AlOMe2 had a more open coordination geometry with a small N-Al-S angle (72.91°) than did TS3c of [OPr-AlOMe2]2, the crowded highest-energy transition state of [OPr-AlOMe2]2 with a larger N-Al-O angle (99.63°).
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Affiliation(s)
- Prasanna Kumar Ganta
- Department of Medicinal and Applied Chemistry, Drug Development and Value Creation Research Center, Kaohsiung Medical University, Kaohsiung, Taiwan, 80708, Republic of China.
| | - Mallemadugula Ravi Teja
- Department of Medicinal and Applied Chemistry, Drug Development and Value Creation Research Center, Kaohsiung Medical University, Kaohsiung, Taiwan, 80708, Republic of China.
| | - Chun-Juei Chang
- Department of Medicinal and Applied Chemistry, Drug Development and Value Creation Research Center, Kaohsiung Medical University, Kaohsiung, Taiwan, 80708, Republic of China.
- Department of International Ph.D. Program for Science, National Sun Yat-sen University, Kaohsiung, Taiwan 80424, Republic of China
| | - Anandan Sambandam
- Nanomaterials and Solar Energy Conversion Lab, Department of Chemistry, National Institute of Technology, Tiruchirappalli, 620015, India
| | - Rajiv Kamaraj
- Department of Medicinal and Applied Chemistry, Drug Development and Value Creation Research Center, Kaohsiung Medical University, Kaohsiung, Taiwan, 80708, Republic of China.
| | - Yu-Ting Chu
- Department of Medicinal and Applied Chemistry, Drug Development and Value Creation Research Center, Kaohsiung Medical University, Kaohsiung, Taiwan, 80708, Republic of China.
- Department of Chemistry, National Sun Yat-Sen University, Kaohsiung, Taiwan, 80424, Republic of China
| | - Shangwu Ding
- Department of Medicinal and Applied Chemistry, Drug Development and Value Creation Research Center, Kaohsiung Medical University, Kaohsiung, Taiwan, 80708, Republic of China.
- Department of Chemistry, National Sun Yat-Sen University, Kaohsiung, Taiwan, 80424, Republic of China
| | - Hsing-Yin Chen
- Department of Medicinal and Applied Chemistry, Drug Development and Value Creation Research Center, Kaohsiung Medical University, Kaohsiung, Taiwan, 80708, Republic of China.
| | - Hsuan-Ying Chen
- Department of Medicinal and Applied Chemistry, Drug Development and Value Creation Research Center, Kaohsiung Medical University, Kaohsiung, Taiwan, 80708, Republic of China.
- Department of Chemistry, National Sun Yat-Sen University, Kaohsiung, Taiwan, 80424, Republic of China
- Department of Medical Research, Kaohsiung Medical University Hospital, Kaohsiung 80708, Taiwan, Republic of China
- National Pingtung University of Science and Technology, Pingtung 91201, Taiwan
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Zeppuhar AN, Falvey DE. Lamp vs Laser: A Visible Light Photoinitiator That Promotes Radical Polymerization at Low Intensities and Cationic Polymerization at High Intensities. J Org Chem 2023. [PMID: 37418315 DOI: 10.1021/acs.joc.3c00636] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/09/2023]
Abstract
A visible light absorbing anthraquinone derivative 1-tosyloxy-2-methoxy-9,10-anthraquinone (QT) mediates both cationic and radical polymerizations depending on the intensity of visible light used. A previous study showed that this initiator generates para-toluenesulfonic acid through a stepwise, two-photon excitation mechanism. Thus, under high-intensity irradiation, QT generates acid in sufficient quantities to catalyze the cationic ring-opening polymerization of lactones. However, under low-intensity (lamp) conditions, the two-photon process is negligible, and QT photooxidizes DMSO, generating methyl radicals which initiate the RAFT polymerization of acrylates. This dual capability was utilized to switch between radical and cationic polymerizations to synthesize a copolymer using a one-pot procedure.
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Affiliation(s)
- Andrea N Zeppuhar
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, United States
| | - Daniel E Falvey
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, United States
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Wannipurage D, D'Aniello S, Pappalardo D, Kulathungage LW, Ward CL, Anderson DP, Groysman S, Mazzeo M. Simple magnesium alkoxides: synthesis, molecular structure, and catalytic behaviour in the ring-opening polymerization of lactide and macrolactones and in the copolymerization of maleic anhydride and propylene oxide. Dalton Trans 2023; 52:8077-8091. [PMID: 37232395 PMCID: PMC11066581 DOI: 10.1039/d3dt00785e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The synthesis of two chiral bulky alkoxide pro-ligands, 1-adamantyl-tert-butylphenylmethanol HOCAdtBuPh and 1-adamantylmethylphenylmethanol HOCAdMePh, is reported and their coordination chemistry with magnesium(II) is described and compared with the coordination chemistry of the previously reported achiral bulky alkoxide pro-ligand HOCtBu2Ph. Treatment of n-butyl-sec-butylmagnesium with two equivalents of the racemic mixture of HOCAdtBuPh led selectively to the formation of the mononuclear bis(alkoxide) complex Mg(OCAdtBuPh)2(THF)2. 1H NMR spectroscopy and X-ray crystallography suggested the selective formation of the C2-symmetric homochiral diastereomer Mg(OCRAdtBuPh)2(THF)2/Mg(OCSAdtBuPh)2(THF)2. In contrast, the less sterically encumbered HOCAdMePh led to the formation of dinuclear products indicating only partial alkyl group substitution. The mononuclear Mg(OCAdtBuPh)2(THF)2 complex was tested as a catalyst in different reactions for the synthesis of polyesters. In the ROP of lactide, Mg(OCAdtBuPh)2(THF)2 demonstrated very high activity, higher than that shown by Mg(OCtBu2Ph)2(THF)2, although with moderate control degrees. Both Mg(OCAdtBuPh)2(THF)2 and Mg(OCtBu2Ph)2(THF)2 were found to be very effective in the polymerization of macrolactones such as ω-pentadecalactone (PDL) and ω-6-hexadecenlactone (HDL) also under mild reaction conditions that are generally prohibitive for these substrates. The same catalysts demonstrated efficient ring-opening copolymerization (ROCOP) of propylene oxide (PO) and maleic anhydride (MA) to produce poly(propylene maleate).
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Affiliation(s)
- Duleeka Wannipurage
- Department of Chemistry, Wayne State University, 5101 Cass Ave., Detroit, MI 48202, USA.
| | - Sara D'Aniello
- Department of Chemistry and Biology "A. Zambelli" University of Salerno, Via Giovanni Paolo II, 132, 84084 Fisciano, SA, Italy.
| | - Daniela Pappalardo
- Dipartimento di Scienze e Tecnologie, Università del Sannio, via de Sanctis snc, 82100 Benevento, Italy
| | | | - Cassandra L Ward
- Lumigen Instrument Center, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, USA
| | - Dennis P Anderson
- Lumigen Instrument Center, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, USA
| | - Stanislav Groysman
- Department of Chemistry, Wayne State University, 5101 Cass Ave., Detroit, MI 48202, USA.
| | - Mina Mazzeo
- Department of Chemistry and Biology "A. Zambelli" University of Salerno, Via Giovanni Paolo II, 132, 84084 Fisciano, SA, Italy.
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