Photofunctional Lanthanoid Complexes, Coordination Polymers, and Nanocrystals for Future Photonic Applications

Abstract

In this account, lanthanoid complexes, coordination polymers, and nanocrystals with photofunctional properties are introduced. To maintain the effective emission of Nd(III), Sm(III), Eu(III), Tb(III), and Yb(III) ions in organic media, the coordination sphere of the lanthanoid ions should consist of strong, bulky, and asymmetric ligands with low vibrational frequencies, that is, there are three criteria for luminescence: 1) suppression of vibrational relaxation, 2) prevention of nonradiative cross relaxation at diffusional collision, and 3) introduction of asymmetric coordination geometry for enhancing electric dipole transition. Lanthanoid coordination compounds with characteristic photosensitizing properties, photochromic properties, circularly polarized luminescence (CPL), metal ion sensing properties, solvent sensing properties, energy-conversion properties, thermostable properties, triboluminescent properties, and thermosensing properties are also described for the development of photofunctional materials. In the second half, the synthesis, photophysical magnetic, and magneto-optical properties of lanthanoid nanocrystals, EuO, EuS, and EuSe, are reported. In particular, the remarkable photophysical properties of nanoaggregates composed of EuS nanocrystals are presented. Photofunctional lanthanoid(III) complexes, coordination polymers, and nanocrystals are expected to open up a frontier field of materials science.

Effective photosensitized, electrosensitized, and mechanosensitized luminescence of lanthanide complexes

“…Therefore, emission transitions yield sharp lines (full-width at half-maximum, FWHM <10 nm) in different spectra, which is a much different result from that seen for semiconductors, transition materials, and organic molecules, as shown in Fig. 1c (in a large-stokes-shift case: FWHM >50 nm) 2,3 . The emission of light radiation for lanthanide(III) ions comes mainly from electric dipole transitions.…”

“…However, the emitting level of lanthanide(III) ion is not changed by the surrounding media, such as an organic ligand and solvent. The emitting levels of the Eu(III), Tb(III), Sm(III), Yb(III), Nd(III) and Er(III) ions have been estimated to be 17,293, 20,500, 17,900, 10,260, 11,100, and 6535 cm −1 , respectively 3 . When the energy level of the T 1 state is lower than that of the emitting level, the lanthanide complex does not emit photons.…”

“…The 4f-4f emissions from Tb(III), Eu(III), and Sm(III) complexes play an important role in the design of monochromatic green, red, and deep-red luminescent materials for displays, lighting, and sensing devices, respectively ( Fig. 2a, b) [3][4][5][6][7][8] . The near-IR 4f-4f luminescence of Nd(III), Er(III), and Yb(III) complexes with long emission lifetimes is useful in bioimaging applications ( Fig.…”

Looking for the Origin of Allosteric Cooperativity in Metallopolymers

“…Metallopolymers are hybrid materials, [1,2] in which metal centers with their specific electronic (optics, magnetism, catalysis) and structural( geometries, coordinationn umbers) properties are incorporated into organic polymers offering easy processabillity,e fficient structuralc ontrol and rich scalability. [3][4][5] In view of their promisinga pplications in light-emitting diodes (LED), [6][7][8][9] in solidc ells for photovoltaics, [10][11][12] in magnetically active [13] and light-emissive liquid crystals [14,15] andi nt elecommunication devices, [16,17] the tuning of their properties by aprecise andc ontrolled metal-loading of the organic scaffold is clearly underexploited. [18,19] Amongt he three possible arrangements of the metal complexes with respect to the polymer backbone,o ften referred to as Wolf-Type I, Type II and Type III (Scheme 1), [20] only the latter,i nw hich the metal centers are incorporated within the polymericn etwork, have been intensively investigatedi nt he fields of coordination polymers and metal-organic frameworks( MOF).…”

“…Ln;L1 N aff;exch;sol of as pecific binding site in the polymer L1 N on the affinity f Ln;L0 aff;exch;sol of the same binding site in monomer L0 [Eq (12)…”