The Role of Vibrational Anharmonicity in the Computational Study of Thermal Spin Crossover
Spin crossover in transition metal complexes can be studied in great detail with computational chemistry. Over the years, the understanding has grown that the relative stability of high-spin (HS) versus low-spin (LS) states is a subtle balance of many factors that all need to be taken into account f...
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| Format: | Article |
| Language: | English |
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MDPI AG
2019-09-01
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| Series: | Magnetochemistry |
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| Online Access: | https://www.mdpi.com/2312-7481/5/3/49 |
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| author | Jianfang Wu Carmen Sousa Coen de Graaf |
| author_facet | Jianfang Wu Carmen Sousa Coen de Graaf |
| author_sort | Jianfang Wu |
| collection | DOAJ |
| description | Spin crossover in transition metal complexes can be studied in great detail with computational chemistry. Over the years, the understanding has grown that the relative stability of high-spin (HS) versus low-spin (LS) states is a subtle balance of many factors that all need to be taken into account for a reliable description. Among the different contributions, the zero-point energy (ZPE) and the entropy play key roles. These quantities are usually calculated assuming a harmonic oscillator model for the molecular vibrations. We investigated the impact of including anharmonic corrections on the ZPE and the entropy and indirectly on the critical temperature of spin crossover. As test systems, we used a set of ten Fe(II) complexes and one Fe(III) complex, covering different coordination modes (mono-, bi-, and tri-dentate ligands), decreasing coordination number upon spin crossover, coordination by second- and third-row atoms, and changes in the oxidation state. The results show that the anharmonicity has a measurable effect, but it is in general rather small, and tendencies are not easily recognized. As a conclusion, we put forward that for high precision results, one should be aware of the anharmonic effects, but as long as computational chemistry is still struggling with other larger factors like the influence of the environment and the accurate determination of the electronic energy difference between HS and LS, the anharmonicity of the vibrational modes is a minor concern. |
| first_indexed | 2024-04-13T07:16:12Z |
| format | Article |
| id | doaj.art-f2aa934a82aa4c06923e3a04e758dc68 |
| institution | Directory Open Access Journal |
| issn | 2312-7481 |
| language | English |
| last_indexed | 2024-04-13T07:16:12Z |
| publishDate | 2019-09-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Magnetochemistry |
| spelling | doaj.art-f2aa934a82aa4c06923e3a04e758dc682022-12-22T02:56:45ZengMDPI AGMagnetochemistry2312-74812019-09-01534910.3390/magnetochemistry5030049magnetochemistry5030049The Role of Vibrational Anharmonicity in the Computational Study of Thermal Spin CrossoverJianfang Wu0Carmen Sousa1Coen de Graaf2Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, Marcel·lí Domingo 1, 43007 Tarragona, Catalonia, SpainDepartament de Ciència de Materials i Química Física, Institut de Química Teòrica i Computacional, Universitat de Barcelona, C/ Martí i Franquès 1, 08028 Barcelona, Catalonia, SpainDepartament de Química Física i Inorgànica, Universitat Rovira i Virgili, Marcel·lí Domingo 1, 43007 Tarragona, Catalonia, SpainSpin crossover in transition metal complexes can be studied in great detail with computational chemistry. Over the years, the understanding has grown that the relative stability of high-spin (HS) versus low-spin (LS) states is a subtle balance of many factors that all need to be taken into account for a reliable description. Among the different contributions, the zero-point energy (ZPE) and the entropy play key roles. These quantities are usually calculated assuming a harmonic oscillator model for the molecular vibrations. We investigated the impact of including anharmonic corrections on the ZPE and the entropy and indirectly on the critical temperature of spin crossover. As test systems, we used a set of ten Fe(II) complexes and one Fe(III) complex, covering different coordination modes (mono-, bi-, and tri-dentate ligands), decreasing coordination number upon spin crossover, coordination by second- and third-row atoms, and changes in the oxidation state. The results show that the anharmonicity has a measurable effect, but it is in general rather small, and tendencies are not easily recognized. As a conclusion, we put forward that for high precision results, one should be aware of the anharmonic effects, but as long as computational chemistry is still struggling with other larger factors like the influence of the environment and the accurate determination of the electronic energy difference between HS and LS, the anharmonicity of the vibrational modes is a minor concern.https://www.mdpi.com/2312-7481/5/3/49spin crossoveriron complexesvibrational frequenciestransition temperatureDFTanharmonicity |
| spellingShingle | Jianfang Wu Carmen Sousa Coen de Graaf The Role of Vibrational Anharmonicity in the Computational Study of Thermal Spin Crossover Magnetochemistry spin crossover iron complexes vibrational frequencies transition temperature DFT anharmonicity |
| title | The Role of Vibrational Anharmonicity in the Computational Study of Thermal Spin Crossover |
| title_full | The Role of Vibrational Anharmonicity in the Computational Study of Thermal Spin Crossover |
| title_fullStr | The Role of Vibrational Anharmonicity in the Computational Study of Thermal Spin Crossover |
| title_full_unstemmed | The Role of Vibrational Anharmonicity in the Computational Study of Thermal Spin Crossover |
| title_short | The Role of Vibrational Anharmonicity in the Computational Study of Thermal Spin Crossover |
| title_sort | role of vibrational anharmonicity in the computational study of thermal spin crossover |
| topic | spin crossover iron complexes vibrational frequencies transition temperature DFT anharmonicity |
| url | https://www.mdpi.com/2312-7481/5/3/49 |
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