A Barrel‐Shaped Metal–Organic Blue‐Box Analogue with Photo‐/Redox‐Switchable Behavior

Abstract

Donor-acceptori nteractionsa re ubiquitous in the design and understanding of host-guest complexes.D espite their non-covalentn ature, they can readily dictate the selfassembly of complex architectures.H ere, ap hoto-/redoxswitchable metal-organic nanocapsule is presented, which was assembled by using lanthanide ions and viologen building blocks, by relyingo ns uch donor-acceptor interactions. The potential of this unique barrel-shaped structure is highlighted for the encapsulation of suitable electron donors, akin to the well-investigated "blue-box" macrocycles. The light-triggeredr eductiono ft he viologen units has been investigated by single-crystal-to-single-crystal X-ray diffraction experiments, complementedb ym agnetic, optical, and solidstate electrochemical characterizations. Density functional theory(DFT) calculations were employed to suggest the most likely electron donor in the light-triggeredr eduction of the viologen-based ligand.

Guest Exchange by a Partial Energy Ratchet in Water

“…EPR spectroscopy showed under UV irradiation ap attern with many couplings typical of av iologen radical cation supporting that aviologen + C radical transiently (Figure 3c). Currently,t he source of the electron donor remains unclear, [81,82] but if at least one electron was to jump from one carboxylate group of PVP 2À ,anegative charge would be removed, thereby decreasing the kinetic barrier for dethreading.W hile methylviologen and its complex with CB [7] showed no EPR signal under UV irradiation, EPR of PVP 2À solutions showed aw eak signal ( Figure S27) suggesting that the benzoate group could be the electron source whereas that of PVP 2À •CB [7] showed ag reen colour and asymmetric EPR spectrum ( Figure S27).…”

Dynamic Manipulating Space‐Resolved Persistent Luminescence in Core–Shell MOFs Heterostructures via Reversible Photochromism

“…The increased absorption in 550-700 nm suggests the generation of pyridine radicals. [39][40][41][42][43][44][45][49][50][51][52][53][54] To further prove such conclusion, electron paramagnetic resonance (EPR) spectra were measured. The EPR spectra (Figure 2 b) show an obvious signal with g = 2.0025 after irradiation but no signal before, illustrating that radicals generate under the light stimulation, which can be attributed to the electron transfer from electron-rich formic acid units to electron-deficient bipy ligands.…”

“…4,4'-bipyridine (4,4'-bipy) is chosen as the ligand, since it has been used as electron acceptor in photochromism, which is prone to achieve electron transfer and generate bipyridine radicals by combining with suitable electron donors. [39][40][41][42][43][44][45][49][50][51][52][53][54] In addition, the Nheterocycles in bipyridine is beneficial to obtain efficient RTP properties. [1-5, 11-18, 21-26, 30-33] A series of MOFs, M-(HCOO) 2 (4,4'-bipy) (M = Zn, MOF-Zn; Cd, MOF-Cd; Co, MOF-Co; Mn, MOF-Mn), have been synthesized, and MOF-Zn/Cd systems exhibit both obvious photochromic and longlived RTP properties: the MOFs present dynamic and tunable persistent luminescence upon photo-stimulus, which show bright yellow afterglow that gradually disappears after further irradiation.…”

“…Benefitting from the introduction of pyridine unit, [39][40][41][42][43][44][45][49][50][51][52][53][54] MOF-Zn exhibits reversible photochromic behavior. As shown in Figures 2 a and S1, the colorless crystal samples turn into blue upon Xe lamp (300 W) irradiation with the optimized wavelength for the coloration process mainly in the range of 310-330 nm.…”

Guest Exchange by a Partial Energy Ratchet in Water

“…EPR spectroscopy showed under UV irradiation ap attern with many couplings typical of av iologen radical cation supporting that aviologen + C radical transiently formed (Figure 3c). Currently,t he source of the electron donor remains unclear, [81,82] but if at least one electron was to jump from one carboxylate group of PVP 2À ,anegative charge would be removed, thereby decreasing the kinetic barrier for dethreading.W hile methylviologen and its complex with CB [7] showed no EPR signal under UV irradiation, EPR of PVP 2À solutions showed aw eak signal ( Figure S27) suggesting that the benzoate group could be the electron source whereas that of PVP 2À •CB [7] showed ag reen colour and asymmetric EPR spectrum ( Figure S27).…”