Pentagonal-bipyramidal Dysprosium(III) complexes with two apical phosphine oxide ligands and equatorial pentadentate N3O2 Schiff-base ligands: Breakdown of the apical magnetic axiality by strong equatorial crystal field†
Tamara A. Bazhenova, Vyacheslav Kopotkov, Denis V. Korchagin, Elena Yureva, Michael V. Zhidkov, Alexey I Dmitriev, Ilya Yakushev, N. N. Efimov, Konstantin Andreevich Babeshkin, Vladimir Sergeevich Mironov, Eduard B. Yagubskii
{"title":"Pentagonal-bipyramidal Dysprosium(III) complexes with two apical phosphine oxide ligands and equatorial pentadentate N3O2 Schiff-base ligands: Breakdown of the apical magnetic axiality by strong equatorial crystal field†","authors":"Tamara A. Bazhenova, Vyacheslav Kopotkov, Denis V. Korchagin, Elena Yureva, Michael V. Zhidkov, Alexey I Dmitriev, Ilya Yakushev, N. N. Efimov, Konstantin Andreevich Babeshkin, Vladimir Sergeevich Mironov, Eduard B. Yagubskii","doi":"10.1039/d4qi02262a","DOIUrl":null,"url":null,"abstract":"A series of three new seven-coordinate pentagonal-bipyramidal (PBPY-7) Dy(III) complexes [Dy(L<small><sup>CH3</sup></small>)(Cy<small><sub>3</sub></small>PO)<small><sub>2</sub></small>]ClO<small><sub>4</sub></small>∙CH<small><sub>3</sub></small>CN (<strong>1</strong>), [Dy(L<small><sup>2(t-Bu)</sup></small>)(Ph<small><sub>3</sub></small>PO)<small><sub>2</sub></small>]ClO<small><sub>4</sub></small>∙0.63C<small><sub>2</sub></small>H<small><sub>5</sub></small>OH (<strong>2</strong>), [Dy(L<small><sup>OCH3</sup></small>)(Ph<small><sub>3</sub></small>PO)<small><sub>2</sub></small>]ClO<small><sub>4</sub></small>∙2H<small><sub>2</sub></small>O (<strong>3</strong>) including various chelating pentadentate ligands with a [N<small><sub>3</sub></small>O<small><sub>2</sub></small>]<small><sup>2−</sup></small> binding node in the equatorial plane, L<small><sup>CH3</sup></small> = [2,6-diacetylpyridine bis(acetylhydrazone)]<small><sup>2-</sup></small>, L<small><sup>2(t-Bu)</sup></small> = [2,6-diacetylpyridine bis(3,5di-tert-butylbenzoylhydrazone)]<small><sup>2-</sup></small>, L<small><sup>CH3</sup></small> = [2,6-diacetylpyridine bis(4-methoxybenzoylhydrazone)]<small><sup>2-</sup></small>, and two apical Cy<small><sub>3</sub></small>PO and Ph<small><sub>3</sub></small>PO ligands was synthesized and characterized structurally and magnetically. AC magnetic measurements indicated a single-molecule-magnet (SMM) behavior of <strong>1</strong>− <strong>3</strong> with energy barriers of <em>U<small><sub>eff</sub></small></em> ≈ 318−350 K. <em>Ab initio</em> calculations and crystal-field (CF) analysis showed that the ground state of <strong>1</strong>− <strong>3</strong> is a nearly pure Ising type Kramers doublet (KD<small><sub>0</sub></small>) |±15/2> <small><sub>eq</sub></small> with the long magnetic axis lying in the equatorial plane N<small><sub>3</sub></small>O<small><sub>2</sub></small>, as opposite to high-performance PBPY-7 Dy(III) SMMs (<em>U<small><sub>eff</sub></small></em> > 1000 K), where long magnetic axis of KD<small><sub>0</sub></small> |±15/2> invariably points toward apical ligands. This difference is due to competition between the apical and equatorial CFs, which has been quantitatevely examined with CF calculations. We show that the turning of the long magnetic axis (<em>g<small><sub>z</sub></small></em> ~ 19.6) from apical ligands (<em>z</em>) to the equatorial plane (<em>xy</em>) is due to crossover between the oblate |±15/2> and prolate |±1/2> ground states of Dy(III) ion, that occurs at the negative ratio <em>B<small><sub>20</sub></small>/B<small><sub>40</sub></small></em> < –0.07 of two axial CF parameters <em>B<small><sub>20</sub></small></em> and <em>B<small><sub>40</sub></small></em>. Complexes <strong>1</strong>−<strong>3</strong> refer to this case due to strong equatorial CF of the negatively charged chelate node [N<small><sub>3</sub></small>O<small><sub>2</sub></small>]<small><sup>2–</sup></small>producing large positive CF parameter <em>B<small><sub>40</sub></small></em> and negative <em>B<small><sub>20</sub></small></em>. In this case, SMM properties of <strong>1</strong>− <strong>3</strong> arise from distortions of the PBPY-7 complex (namely, from a large O1-Dy-O2 bond angle of ~ 100<small><sup>o</sup></small> in the N<small><sub>3</sub></small>O<small><sub>2</sub></small> pentagon of <strong>1</strong>−<strong>3</strong>) that mix the lowest state |±1/2> and low-lying low-<em>m<small><sub>J</sub></small></em> states to produce the equatorial KD<small><sub>0</sub></small> |±15/2><small><sub>eq</sub></small>. This highlights a breakdown of the apical magnetic axiality, since the SMM performance of <strong>1</strong>− <strong>3</strong> is governed by a strong equatorial CF and distortions rather than by high <em>D<small><sub>5h</sub></small></em> symmetry and strong apical ligands. Some ways to improve the SMM efficiency of <strong>1</strong>−<strong> 3</strong> and related PBPY-7 Dy(III) complexes are discussed.","PeriodicalId":79,"journal":{"name":"Inorganic Chemistry Frontiers","volume":null,"pages":null},"PeriodicalIF":6.1000,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Inorganic Chemistry Frontiers","FirstCategoryId":"92","ListUrlMain":"https://doi.org/10.1039/d4qi02262a","RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"CHEMISTRY, INORGANIC & NUCLEAR","Score":null,"Total":0}
引用次数: 0
Abstract
A series of three new seven-coordinate pentagonal-bipyramidal (PBPY-7) Dy(III) complexes [Dy(LCH3)(Cy3PO)2]ClO4∙CH3CN (1), [Dy(L2(t-Bu))(Ph3PO)2]ClO4∙0.63C2H5OH (2), [Dy(LOCH3)(Ph3PO)2]ClO4∙2H2O (3) including various chelating pentadentate ligands with a [N3O2]2− binding node in the equatorial plane, LCH3 = [2,6-diacetylpyridine bis(acetylhydrazone)]2-, L2(t-Bu) = [2,6-diacetylpyridine bis(3,5di-tert-butylbenzoylhydrazone)]2-, LCH3 = [2,6-diacetylpyridine bis(4-methoxybenzoylhydrazone)]2-, and two apical Cy3PO and Ph3PO ligands was synthesized and characterized structurally and magnetically. AC magnetic measurements indicated a single-molecule-magnet (SMM) behavior of 1− 3 with energy barriers of Ueff ≈ 318−350 K. Ab initio calculations and crystal-field (CF) analysis showed that the ground state of 1− 3 is a nearly pure Ising type Kramers doublet (KD0) |±15/2> eq with the long magnetic axis lying in the equatorial plane N3O2, as opposite to high-performance PBPY-7 Dy(III) SMMs (Ueff > 1000 K), where long magnetic axis of KD0 |±15/2> invariably points toward apical ligands. This difference is due to competition between the apical and equatorial CFs, which has been quantitatevely examined with CF calculations. We show that the turning of the long magnetic axis (gz ~ 19.6) from apical ligands (z) to the equatorial plane (xy) is due to crossover between the oblate |±15/2> and prolate |±1/2> ground states of Dy(III) ion, that occurs at the negative ratio B20/B40 < –0.07 of two axial CF parameters B20 and B40. Complexes 1−3 refer to this case due to strong equatorial CF of the negatively charged chelate node [N3O2]2–producing large positive CF parameter B40 and negative B20. In this case, SMM properties of 1− 3 arise from distortions of the PBPY-7 complex (namely, from a large O1-Dy-O2 bond angle of ~ 100o in the N3O2 pentagon of 1−3) that mix the lowest state |±1/2> and low-lying low-mJ states to produce the equatorial KD0 |±15/2>eq. This highlights a breakdown of the apical magnetic axiality, since the SMM performance of 1− 3 is governed by a strong equatorial CF and distortions rather than by high D5h symmetry and strong apical ligands. Some ways to improve the SMM efficiency of 1− 3 and related PBPY-7 Dy(III) complexes are discussed.