Cationic and anionic cage compounds can show unique molecular recognition capabilities as a consequence of their ionic nature. [1] In contrast, radical cages with unpaired electron spins in their frameworks are seldom prepared and their properties-with the exception of cagelike cluster compounds that have unpaired electrons at metal centersparticularly the interactions with radical guests, are largely unexplored.[2] This is mainly because of difficulties in introducing stable organic radicals at the core of the host frameworks. Here we report the facile self-assembly of a radical cage containing multiple spin centers around a cavity suitable for guest inclusion. We show that verdazyl radical-cored ligand 1 is quantitatively self-assembled into the large M 6 L 4 spin cage 2 upon treatment with a Pd II complex (Scheme 1). Similar to the analogous triazine-cored M 6 L 4 complexes, [3] spin cage 2 is capable of binding neutral guests within the cavity in aqueous media. When radical guests are accommodated in the cavity of 2, spin-spin interactions between the host and the guest are observed. We thus obtain a unique spin cage whose magnetic properties can be modulated by inclusion of a radical guest.Verdazyl radical ligand 1 was prepared by modified literature procedures (Scheme 2).[4] When a mixture of 1 (8 mmol) and [Pd(bpy)(NO 3 ) 2 ] (bpy = 2,2'-bipyridyl, 12 mmol) was stirred in water (2 mL) at room temperature for 2 h, the M 6 L 4 complex 2 formed quantitatively, as indicated by CSI-MS and ESR studies.[5] After counterion exchange with PF 6 À ions, CSI-MS measurements showed a series of prominent signals corresponding to [2-(PF 6, from which the molecular weight of 2 (PF 6 salt) was determined to be 4580.2 Da (calculated as 4580.5 Da). After cage 2 had been decomplexed with base, the amount of radicals in the recovered ligand was measured to be 1.0, thus indicating that the radical does not degrade during the complexation and decomplexation. [6] The structure of 2 was fully characterized by X-ray crystallographic analysis. Single crystals of 2 were obtained by the slow vapor diffusion of acetone into an aqueous solution of 2.[7] The verdazyl panels are disordered and indistinguishable, as the C 2v symmetry of ligand 1 generates ten possible structural isomers. For clarity, only one of the isomers is shown in Figure 1. Although it involves severe disorder, the
Redetermination of the crystal structure of poly(p‐benzamide) was made by using newly collected intensity data. The molecular conformation is TCTC, where the internal rotation angles about the NC bond of the amide group and about the virtual bond of N‐phenyl‐C are T (trans) and C (cis) conformations, respectively. Two molecular chains pass through a rectangular unit cell with dimension, a = 7.75 Å, b = 5.30 Å, c (fiber axis) = 12.87 Å, and the space group, P212121‐D 42. The reflection observed at the spacing of 010 may be attributed to the reflection due to another crystal polymorph or the diffuse scattering due to disorder. © 1993 John Wiley & Sons, Inc.
A large organic ionic crystal (10×28×15 mm3):4-nitrophenol sodium(:Na) salt dihydrate (NPNa) crystal, which had good optical, mechanical, and thermal properties, was grown for the second-harmonic generation (SHG) device. Its effective nonlinear constant was found to be 5.0 pm/V at 1064 nm. The Vickers hardness and thermal conductivity were about two times larger than those of molecular crystals. The SHG device made of DNPNa, in which the water of crystallization of NPNa was deuterated, was used for the intracavity SHG of a diode-pumped cw Nd:YVO4 laser. High SHG power of 4.4 mW at 532 nm was obtained for the first time with an organic nonlinear material.
A prism-shaped spin cage, in which two radical panels were aligned in a face-to-face fashion at a distance of 6.8 A, efficiently induced through-space metal-radical spin-spin interaction by encapsulation of a planar copper complex.
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