Research on single-crystal-to-single-crystal photoaddition and extension of Schmidt's rule in topological chemistry

Xiao, Changchun; Deng, Xi‐Ling; Wei, Ziheng; Yang, Shi‐Yao

doi:10.1039/d3ce00443k

“…While these postulates have served as the guiding principle for the rational design of molecular crystals for many successful topochemical reactions, [17–23] there are examples of inert crystals despite satisfying topochemical postulates [24–28] . There are also many topochemically reactive crystals that do not meet these criteria [29–36] . Such reactivity is due to various stimuli‐induced molecular motions, within the crystal lattice, leading to the transient attainment of reactive arrangements.…”

Section: Figurementioning

confidence: 99%

“…[24][25][26][27][28] There are also many topochemically reactive crystals that do not meet these criteria. [29][30][31][32][33][34][35][36] Such reactivity is due to various stimuli-induced molecular motions, within the crystal lattice, leading to the transient attainment of reactive arrangements. However, in all these cases, the molecules undergo various motions to attain a reactive orientation due to the absence of a pre-existing favorable arrangement satisfying Schmidt's criteria.…”

mentioning

confidence: 99%

Massive Molecular Motion in Crystal Leads to an Unexpected Helical Covalent Polymer in a Solid‐state Polymerization

Khazeber,

Kana,

Sureshan

2024

Angew Chem Int Ed

7

0

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We designed a proline‐derived monomer with azide and alkene functional groups to enable topochemical ene‐azide cycloaddition (TEAC) polymerization. In its crystal, the monomer forms supramolecular helices along the 'a' axis through various non‐covalent interactions. Along the 'c' axis, the molecules arrange themselves head‐to‐tail in a wave‐like pattern, positioning the azide and alkene groups of adjacent molecules in close proximity and anti‐parallel orientation, complying with Schmidt's criteria for topochemical reaction. This prearranged configuration was expected to facilitate smooth topochemical polymerization, resulting in a 1,4‐triazoline‐linked polymer. Upon heating, the monomer underwent TEAC polymerization in a remarkable single‐crystal‐to‐single‐crystal fashion, but, to our surprise, it yielded an unexpected covalent helical polymer linked by 1,5‐disubstituted triazoline units. Remarkably, the crystal avoids the ready‐to‐react arrangement for polymerization, but connects monomer molecules within the supramolecular helix through the cycloaddition of azide and alkene groups, even though they are not in close proximity nor in the expected orientation. This unexpected path, involving a substantial 134° rotation of the alkene group, yields hitherto unknown 1,5‐disubstituted triazoline product regiospecifically. This study serves as a cautionary reminder that relying solely on topochemical postulates for predicting reactivity can sometimes be misleading.

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“…While these postulates have served as the guiding principle for the rational design of molecular crystals for many successful topochemical reactions, [17–23] there are examples of inert crystals despite satisfying topochemical postulates [24–28] . There are also many topochemically reactive crystals that do not meet these criteria [29–36] . Such reactivity is due to various stimuli‐induced molecular motions, within the crystal lattice, leading to the transient attainment of reactive arrangements.…”

Section: Figurementioning

confidence: 99%

“…[24][25][26][27][28] There are also many topochemically reactive crystals that do not meet these criteria. [29][30][31][32][33][34][35][36] Such reactivity is due to various stimuli-induced molecular motions, within the crystal lattice, leading to the transient attainment of reactive arrangements. However, in all these cases, the molecules undergo various motions to attain a reactive orientation due to the absence of a pre-existing favorable arrangement satisfying Schmidt's criteria.…”

mentioning

confidence: 99%

Massive Molecular Motion in Crystal Leads to an Unexpected Helical Covalent Polymer in a Solid‐state Polymerization

Khazeber,

Kana,

Sureshan

2024

Angewandte Chemie

1

0

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We designed a proline‐derived monomer with azide and alkene functional groups to enable topochemical ene‐azide cycloaddition (TEAC) polymerization. In its crystal, the monomer forms supramolecular helices along the 'a' axis through various non‐covalent interactions. Along the 'c' axis, the molecules arrange themselves head‐to‐tail in a wave‐like pattern, positioning the azide and alkene groups of adjacent molecules in close proximity and anti‐parallel orientation, complying with Schmidt's criteria for topochemical reaction. This prearranged configuration was expected to facilitate smooth topochemical polymerization, resulting in a 1,4‐triazoline‐linked polymer. Upon heating, the monomer underwent TEAC polymerization in a remarkable single‐crystal‐to‐single‐crystal fashion, but, to our surprise, it yielded an unexpected covalent helical polymer linked by 1,5‐disubstituted triazoline units. Remarkably, the crystal avoids the ready‐to‐react arrangement for polymerization, but connects monomer molecules within the supramolecular helix through the cycloaddition of azide and alkene groups, even though they are not in close proximity nor in the expected orientation. This unexpected path, involving a substantial 134° rotation of the alkene group, yields hitherto unknown 1,5‐disubstituted triazoline product regiospecifically. This study serves as a cautionary reminder that relying solely on topochemical postulates for predicting reactivity can sometimes be misleading.

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“…Comparing the two structures before and after the [2 + 2] photocycloaddition reaction, the students should observe the formation of the cyclobutane derived from pairs of CC bonds (Figure ). It is important to engage students in the discussion of the potential reason for the cyclobutane formation of the CC bonds, which may be due to the fact that the pedal motion in the crystal structure brings the CC bonds of adjacent 4-npy ligands parallel to each other so that a photochemical [2 + 2] cycloaddition can occur. − …”

Section: Description Of the Experimentsmentioning

confidence: 99%

Synthesis, Structural Characterization, and Photochemical [2 + 2] Cycloaddition of a Coordination Polymer: Multiweek Inorganic–Organic Chemistry Experiments

Hong,

Wang,

Ge

et al. 2023

J. Chem. Educ.

0

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The [2 + 2] photocycloaddition reaction of olefins is an effective, atom-economical approach to produce cyclobutane compounds in organic synthetic chemistry, and they usually exhibit high regioselectivity and stereoselectivity. Here we devised a solid-state [2 + 2] photocycloaddition experiment that introduces senior undergraduate students with the principles of coordination chemistry, organic chemistry, structural chemistry, and supramolecular chemistry, which have been widely used in material chemistry, catalysis, nanotechnology, and other fields. The experiment employs coordination interactions that act as templates to directing the [2 + 2] photocycloaddition reaction. A photoreactive coordination polymer [Zn(oba)(4-npy)] 2 •(4-npy) 0.25 (1, 4-npy = (E)-4-(2-(naphthalen-1-yl)vinyl)pyridine, H 2 oba = 4,4′-oxidibenzoic acid) is solvothermally prepared and undergoes a [2 + 2] photocycloaddition reaction, affording the new compound [Zn 2 (oba) 2 (HTpncb)](4-npy) 0.25 (1a, HT-pncb = rctt−1,3-bis(4-pyridyl)-2,4-bis(1-naphthyl)cyclobutane; HT = head-to-tail) upon UV light illumination. The experiments will strengthen the students' experimental skills while the diverse characterization experiments will allow them to experience the contribution of each method and their complementarity in monitoring the structural changes that occur upon photoreaction. This comprehensive project will help students broaden the research horizon, cultivate research skills, follow strict scientific procedures, and promote rigorous thinking in a laboratory course.

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Research on single-crystal-to-single-crystal photoaddition and extension of Schmidt's rule in topological chemistry

Abstract: In this thesis, we report the synthesis of a MOF containing multiple C=C bonds geometrical features by adjusting the reactant ratio of the synthetic system. The photochemical addition studies have...

Cited by 6 publications

References 31 publications

Massive Molecular Motion in Crystal Leads to an Unexpected Helical Covalent Polymer in a Solid‐state Polymerization

Massive Molecular Motion in Crystal Leads to an Unexpected Helical Covalent Polymer in a Solid‐state Polymerization

Massive Molecular Motion in Crystal Leads to an Unexpected Helical Covalent Polymer in a Solid‐state Polymerization

Synthesis, Structural Characterization, and Photochemical [2 + 2] Cycloaddition of a Coordination Polymer: Multiweek Inorganic–Organic Chemistry Experiments

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