Light Switches the Ligand! Photochromic Azobenzene–Phosphanes

Segarra‐Maset, Maria Dolores; Leeuwen, Piet W. N. M. van; Freixa, Zoraida

doi:10.1002/ejic.201000063

Cited by 41 publications

(32 citation statements)

References 29 publications

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“…These reactions were performed by heating the substrates mixtures at 100–135 °C in the presence of Pd(OAc) 2 . The same strategy and analogous conditions allowed the synthesis of the ester‐functionalized phosphines 13 [22] and the parent para‐ and meta ‐phosphines 6 a and 14 a [18a] (Scheme 6c). These few examples show that, despite the rather harsh conditions, the method tolerates the diazo unit as well as the presence of functional groups.…”

Section: Synthesis Of Photoswitchable Phosphinesmentioning

confidence: 99%

Photoswitchable phosphines in catalysis

et al. 2020

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Section: Synthesis Of Photoswitchable Phosphinesmentioning

confidence: 99%

Photoswitchable phosphines in catalysis

et al. 2020

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“…Typically, yields are quite low (max. 53 %22 for the para position, 47 % for the ortho position, and 54 %28 for the meta position). The reason for these poor yields is the low tolerance of the azo group towards reductive conditions: in competition with halogen–lithium exchange, nucleophilic attack by the alkyl lithium species on the azo group leads to hydrazine analogues of the starting material 3 and 4 and, after quenching with trimethylsilyl bromide (TMSBr), 6 and 7 (Scheme ) 29–33…”

Section: Introductionmentioning

confidence: 98%

High‐Yield Lithiation of Azobenzenes by Tin–Lithium Exchange

Strueben

Lipfert

Springer

et al. 2015

Chemistry A European J

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The lithiation of halogenated azobenzenes by halogen-lithium exchange commonly leads to substantial degradation of the azo group to give hydrazine derivatives besides the desired aryl lithium species. Yields of quenching reactions with electrophiles are therefore low. This work shows that a transmetalation reaction of easily accessible stannylated azobenzenes with methyllithium leads to a near-quantitative lithiation of azobenzenes in para, meta, and ortho positions. To investigate the scope of the reaction, various lithiated azobenzenes were quenched with a variety of electrophiles. Furthermore, mechanistic (119) Sn NMR spectroscopic studies on the formation of lithiated azobenzenes are presented. A tin ate complex of the azobenzene was detected and characterized at low temperature.

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“…There are several classifications of star-shaped azos: they may differ in (i) the number of arms (three [9,10,[14][15][16][17][18][19][20], four [7,21,22], six [23][24][25], nine [26]), (ii) in their centres (nitrogen [9,19], phosphorus [27], silicon [28] or carbon atoms [21,22], benzene [14,16,20,[29][30][31][32], polycyclic aromatic hydrocarbons [25,33], heterocyclic hydrocarbons [34][35][36][37], some chiral groups [6] or bio-active residues [38]), (iii) in the way azobenzenes are attached to the centre (covalently or noncovalently [39]), (iv) in their conformational rigidity (flexible or rigid), (v) in their overall geometry (quasi-planar or 3D). Both the conformational rigidity and the shape of the star are closely related to the chemical nature of the star core, for instance, the planar conjugated fragment in the absence of any fatty linkers between the centre and the azobenzene arms supports the planarity of the star and its rigidity, and vice versa, long hydrocarbon linkers provokes its conformational flexibility [8,30,31].…”

Section: Introductionmentioning

confidence: 99%

Stacks of Azobenzene Stars: Self-Assembly Scenario and Stabilising Forces Quantified in Computer Modelling

Savchenko

Koch

Pavlov

et al. 2019

Preprint

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In this paper, the columnar supramolecular aggregates of photosensitive star-shaped azobenzenes with benzene-1,3,5-tricarboxamide core and azobenzene arms are analysed theoretically applying a combination of computer simulation techniques. Without a light stimulus, the trans-stars build one-dimensional columns of stacked molecules during the first stage of the noncovalent association. These columnar aggregates represent the structural elements of more complex experimentally observed morphologies -- fibers, spheres, gels and others. Upon UV light exposure, the azobenzene arms isomerise from thermodynamically stable planar trans- to a metastable kinked cis-state influencing the aggregate morphology. Here, we determine the most favourable mutual orientations of the \textit{trans}-stars in the stack in terms of (i) the pi-pi distance between the cores lengthwise the aggregate, (ii) the star slipped displacements and (iii) the rotation promoting the helical twist and chirality of the aggregate by calculating the binding energy diagrams using density functional theory. The model predictions are further compared with available experimental data. The intermolecular forces responsible for the stability of the stacks made of trans-azobenzene stars in crystals are quantified using Hirshfeld surface analysis. Finally, to characterize the self-assembly mechanism of such stars in solution, we calculate the hydrogen bond lengths, the normalized dipole moment and the binding energies as the functions of the columnar length using molecular dynamics trajectories, and conclude about the cooperative nature of this process.

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Light Switches the Ligand! Photochromic Azobenzene–Phosphanes

Abstract: Three phosphanes containing azobenzene groups were synthesized, and the photochemical behaviour of their platinum complexes was studied by using the light‐induced (E)/(Z) isomerization as a switch to change ligand properties.

Cited by 41 publications

References 29 publications

Photoswitchable phosphines in catalysis

Photoswitchable phosphines in catalysis

High‐Yield Lithiation of Azobenzenes by Tin–Lithium Exchange

Stacks of Azobenzene Stars: Self-Assembly Scenario and Stabilising Forces Quantified in Computer Modelling

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