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Shil S, Bhattacharya D, Misra A, Bytautas L. Antiaromatic Molecules as Magnetic Couplers: A Computational Quest. J Phys Chem A 2024; 128:815-828. [PMID: 38267395 PMCID: PMC10860145 DOI: 10.1021/acs.jpca.3c05784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Revised: 12/28/2023] [Accepted: 01/03/2024] [Indexed: 01/26/2024]
Abstract
In this study, we investigate a set of organic diradical structures in which two oxo-verdazyl radicals are selected as radical spin centers that are connected (coupled) via six coupler molecules (CM), resulting in various magnetic (ferromagnetic (FM) or antiferromagnetic (AFM)) characteristics, as reflected by their exchange coupling constants (J). We have designed 12 diradicals with 6-antiaromatic couplers coupled with bis-oxo-verdazyl diradicals with meta-meta (m-m) and para-meta (p-m) positional connectivities. The nature of the magnetic coupling (ferromagnetic, nonmagnetic, or antiferromagnetic) and the magnitude of the exchange constant J depend on the type of coupler, the connecting point between each radical center and CM, the degree of aromaticity of the coupler, and the length of the through-bond distance between radical centers. The computed magnetic exchange coupling constants J for these diradicals at the B3LYP/6-311++G(d,p) and MN12SX/6-311++G(d,p) levels of theory are large for many of these structures, indicating strong ferromagnetic coupling (with positive J values). In some cases, magnetic couplings are observed with J > 1000 cm-1 (B3LYP/6-311++G(d,p)) and strong antiferromagnetic coupling (with negative J values) with J < -1000 cm-1 (B3LYP/6-311++G(d,p)). Similarly, in some cases, magnetic couplings are observed with J > 289 cm-1 (MN12SX/6-311++G(d,p)) and strong antiferromagnetic coupling (with negative J values) with J < -568 cm-1 (MN12SX/6-311++G(d,p)). Furthermore, while numerous studies have reported that the degree of aromaticity of molecular couplers often favors strong ferromagnetic coupling, displaying the high-spin character of diradicals in their ground states, the couplers chosen in this study are characterized as antiaromatic or nonaromatic. The current investigation provides evidence that, remarkably, antiaromatic couplers are able to enhance stability by favoring electronic diradical structures with very strong ferromagnetic coupling when the length of the through-bond distance and connectivity pattern between radical centers are selected in such a way that the FM coupling is optimized. The findings in this study offer new strategies in the design of novel organic materials with interesting magnetic properties for practical applications.
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Affiliation(s)
- Suranjan Shil
- Manipal
Centre for Natural Sciences (Centre of Excellence), Manipal Academy of Higher Education, Manipal 576104, India
| | | | - Anirban Misra
- Department
of Chemistry, University of North Bengal, Raja Rammohunpur, Siliguri 734013, India
| | - Laimutis Bytautas
- Department
of Chemistry, Galveston College, 4015 Avenue Q, Galveston, Texas 77550, United States
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Shen L, Gao X, Chang Z, Zhang C, Li Y, Lu J, Meng Q, Wu Q. Sufficient driving force for quinoidal isoindigo-based diradicaloids with tunable diradical characters. Phys Chem Chem Phys 2024; 26:2529-2538. [PMID: 38170813 DOI: 10.1039/d3cp05199d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Stable organic π-conjugated diradcialoids with tunable diradical characters can profoundly affect emerging technology. Over the past years, great efforts have been devoted to studying the structure-diradical character relationship in diradicaloids. Herein, a series of quinoidal isoindigo (IID) compounds with different attached terminal end groups were designed. Detailed analysis focuses on elucidating the driving force for evoking and enhancing the diradical character in the quinoidal IID systems. The arylene units of the IID core and the bridged aromatic units determine the contribution of the open-shell diradical form in the ground state. Diradical character y0 correlates well with bond length alternation (BLA), the total HOMA, and the total NICS(1)zz, and it is tuned by bridged aromatic units and terminal end groups in symmetric systems. The zwitterionic character weakens the diradical character in asymmetric systems to different extents. This work contributes to the deep understanding of evoking and enhancing the diradical character in quinoidal IID-based diradcialoids, providing useful guidelines to produce new molecules with desirable properties.
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Affiliation(s)
- Li Shen
- College of Chemical Engineering and Environmental Chemistry, Weifang University, Weifang, 261061, China.
| | - Xiaobo Gao
- College of Chemical Engineering and Environmental Chemistry, Weifang University, Weifang, 261061, China.
| | - Zhanqing Chang
- College of Chemical Engineering and Environmental Chemistry, Weifang University, Weifang, 261061, China.
| | - Changhao Zhang
- College of Chemical Engineering and Environmental Chemistry, Weifang University, Weifang, 261061, China.
| | - Yue Li
- College of Chemical Engineering and Environmental Chemistry, Weifang University, Weifang, 261061, China.
| | - Jitao Lu
- College of Chemical Engineering and Environmental Chemistry, Weifang University, Weifang, 261061, China.
| | - Qingguo Meng
- College of Chemical Engineering and Environmental Chemistry, Weifang University, Weifang, 261061, China.
| | - Qian Wu
- College of Chemical Engineering and Environmental Chemistry, Weifang University, Weifang, 261061, China.
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Miller PD, Shultz DA, Mengell J, Kirk ML, Wojtas L. Variation from closed-shell to open shell electronic structures in oligothiophene bis(dioxolene) complexes. Chem Sci 2023; 14:12264-12276. [PMID: 37969598 PMCID: PMC10631215 DOI: 10.1039/d3sc02341a] [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: 05/05/2023] [Accepted: 10/07/2023] [Indexed: 11/17/2023] Open
Abstract
A series of oligothiophene bis(dioxolene) complexes, SQ-Thn-SQ (SQ = S = ½TpCum,MeZnII(3-tert-butyl-orthosemiquinonate); TpCum,Me = tris(5-cumenyl-3-methylpyrazolyl)borate anion) have been synthesized, structurally characterized, and studied as a function of the number of thiophene bridging units, n (n = 0-3) using a combination of variable-temperature (VT) electronic absorption and EPR spectroscopies, and VT magnetic susceptibility measurements. The thiophene bridge bond lengths determined by X-ray crystallography display dramatic differences across the SQ-Thn-SQ series. Bridge bond deviation values (Σ|Δi|) display a progressive change in the nature of the bridge fragment bonding as the number of thiophene groups increases, with quinoidal bridge character for n = 1 (SQ-Th-SQ) and biradical character with "aromatic" bridge bond lengths for n = 3 (SQ-Th3-SQ). Remarkably, for n = 2 (SQ-Th2-SQ) the nature of the bridge fragment is intermediate between quinoid and biradical aromatic, which we describe as having open-shell character as opposed to biradicaloid since the open-shell biradical configuration does not have the correct symmetry to mix with the quinoidal ground-state configuration. This bridge bonding character is reflected in the energies of the lowest lying open-shell states for these three molecules. The SQ-Th-SQ molecule is diamagnetic at all temperatures studied, and we provide evidence for SQ-SQ antiferromagnetic exchange coupling and population of triplet states in SQ-Th2-SQ and SQ-Th3-SQ, with JSQ-SQ(ave) = -279 cm-1 (VT EPR/electronic absorption/magnetic susceptibility) and JSQ-SQ = -117 cm-1 (VT EPR/electronic absorption/magnetic susceptibility), respectively. The results have been interpreted in the context of state configurational mixing within a simplified 4-electron, 3-orbital model that explicitly contains contributions of a bridge fragment. Variable-temperature spectroscopic- and magnetic susceptibility data are consistent with two low-lying open-shell states for SQ-Th3-SQ, but three low-lying states (one closed-shell and two open-shell) for SQ-Th2-SQ. This model provides a simple symmetry-based framework to understand the continuum of electronic and geometric structures of this class of molecules as a function of the number of thiophene units in the bridge.
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Affiliation(s)
- Paul D Miller
- Department of Chemistry, North Carolina State University Raleigh North Carolina 27695-8204 USA
| | - David A Shultz
- Department of Chemistry, North Carolina State University Raleigh North Carolina 27695-8204 USA
| | - Joshua Mengell
- Department of Chemistry and Chemical Biology, The University of New Mexico MSC03 2060, 1 University of New Mexico Albuquerque NM 87131-0001 USA
| | - Martin L Kirk
- Department of Chemistry and Chemical Biology, The University of New Mexico MSC03 2060, 1 University of New Mexico Albuquerque NM 87131-0001 USA
- The Center for High Technology Materials, The University of New Mexico Albuquerque New Mexico 87106 USA
- Center for Quantum Information and Control (CQuIC), The University of New Mexico Albuquerque New Mexico 87131-0001 USA
| | - Lukasz Wojtas
- Department of Chemistry, University of South Florida 4202 E. Fowler Avenue, CHE 205 Tampa FL 33620-5250 USA
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Ji Y, Moles Quintero S, Dai Y, Marín-Beloqui JM, Zhang H, Zhan Q, Sun F, Wang D, Li X, Wang Z, Gu X, Negri F, Casado J, Zheng Y. 77 % Photothermal Conversion in Blatter-Type Diradicals: Photophysics and Photodynamic Applications. Angew Chem Int Ed Engl 2023; 62:e202311387. [PMID: 37650244 DOI: 10.1002/anie.202311387] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2023] [Revised: 08/28/2023] [Accepted: 08/29/2023] [Indexed: 09/01/2023]
Abstract
Diradicals based on the Blatter units and connected by acetylene and alkene spacers have been prepared. All the molecules show sizably large diradical character and low energy singlet-triplet gaps. Their photo-physical properties concerning their lowest energy excited state have been studied in detail by steady-state and time-resolved absorption spectroscopy. We have fully identified the main optical absorption band and full absence of emission from the lowest energy excited state. A computational study has been also carried out that has helped to identify the presence of a conical intersection between the lowest energy excited state and the ground state which produces a highly efficient light-to-heat conversion of the absorbed radiation. Furthermore, an outstanding photo-thermal conversion 77.23 % has been confirmed, close to the highest in the diradicaloid field. For the first time, stable diradicals are applied to photo-thermal therapy of tumor cells with good stability and satisfactory performance at near-infrared region.
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Affiliation(s)
- Yu Ji
- School of Optoelectronic Science and Engineering, University of Electronic Science and Technology of China (UESTC), Chengdu, 610054, P. R. China
| | - Sergio Moles Quintero
- Department of Physical Chemistry, University of Málaga, Campus de Teatinos s/n, 29071, Málaga, Spain
| | - Yasi Dai
- A Dipartimento di Chimica 'Giacomo Ciamician', Università di Bologna, Via F. Selmi, 2, 40126, Bologna, Italy
- INSTM, UdR Bologna, Via F. Selmi, 2, 40126, Bologna, Italy
| | - Jose M Marín-Beloqui
- Department of Physical Chemistry, University of Málaga, Campus de Teatinos s/n, 29071, Málaga, Spain
| | - Hanjun Zhang
- School of Optoelectronic Science and Engineering, University of Electronic Science and Technology of China (UESTC), Chengdu, 610054, P. R. China
| | - Qian Zhan
- School of Optoelectronic Science and Engineering, University of Electronic Science and Technology of China (UESTC), Chengdu, 610054, P. R. China
| | - Fanxi Sun
- School of Optoelectronic Science and Engineering, University of Electronic Science and Technology of China (UESTC), Chengdu, 610054, P. R. China
| | - Dongsheng Wang
- School of Optoelectronic Science and Engineering, University of Electronic Science and Technology of China (UESTC), Chengdu, 610054, P. R. China
| | - Xiangkun Li
- Spin-X Institute, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou, 510641, P. R. China
| | - Zhiyi Wang
- Spin-X Institute, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou, 510641, P. R. China
| | - Xinggui Gu
- Beijing Advanced Innovation Center for Soft Matter Science and Engineering, College of Materials Science and Engineering, State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing, 100029, P. R. China
| | - Fabrizia Negri
- A Dipartimento di Chimica 'Giacomo Ciamician', Università di Bologna, Via F. Selmi, 2, 40126, Bologna, Italy
- INSTM, UdR Bologna, Via F. Selmi, 2, 40126, Bologna, Italy
| | - Juan Casado
- Department of Physical Chemistry, University of Málaga, Campus de Teatinos s/n, 29071, Málaga, Spain
| | - Yonghao Zheng
- School of Optoelectronic Science and Engineering, University of Electronic Science and Technology of China (UESTC), Chengdu, 610054, P. R. China
- State Key Laboratory of Organic Electronics and Information Displays & Institute of Advanced Materials(IAM), Nanjing University of Posts & Telecommunications, 9 Wenyuan Road, Nanjing, 210023, P. R. China
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