Youn-Doo Kim

Determination of the structure of EuTETA and the luminescence properties of EuTETA and EuDOTA (TETA=1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetraacetate and DOTA=1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate)

Abstract The crystal structure and the luminescence of the complex Na[Eu(TETA)]·2H2O·4NaCl (TETA=1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetraacetate) have been determined. The space group is P 1 , and the lattice parameters are a=9.283(2) A, b=17.794(3) A, c=19.8087(17) A, α=70.733(11)°, β=83.474(12)°, γ=88.478(18)°, V=3068.6(9) A3, ρ=1.890 g cm−3, and Z=2. The luminescence of Na[EuDOTA·H2O]·3H2O (DOTA=1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate) has also been reported. In the TETA macrocycle, the Eu(III) is completely encapsulated via coordination to the four nitrogen atoms and the four carboxylate oxygen atoms of the ligand. The geometry of the eight-coordinate polyhedron is a strongly distorted dodecahedron. The characteristic feature in the geometry is the conformation of the pendant carboxylate arms. The asymmetric unit consists of two independent molecules, differentiated from the helicities of the pendant arms. When the EuTETA and EuDOTA crystals are excited by UV light, they produce very characteristic luminescences responsible for the 5D0→7FJ (J=0, 1, 2, 3, 4) transitions. Unlike the EuDOTA complex, the luminescence structure of the EuTETA complex is significantly affected by the crystalline state. This might be due to the rigidity of the complex. The energy-level schemes of the 7FJ states and detailed assignments for the observed luminescence lines of the EuTETA and EuDOTA complexes have been proposed by phenomenological simulation in the framework of the crystal-field Hamiltonian.

Luminescence and crystal-field parameters of Eu(III) and Tb(III) complexes with nitrilotriacetate

Luminescence spectra of [Eu(NTA)2·H2O]3− and [Tb(NTA)2·H2O]3− crystals measured at 78.8 K are reported. When the crystals are excited by UV light, they produce very characteristic luminescence lines in the 580–720 nm region for [Eu(NTA)2·H2O]3− and in the 450–700 nm region for [Tb(NTA)2·H2O]3−. The energy-level schemes of the 7FJ states and the emitting level for Eu(III) and Tb(III) ions have been proposed by phenomenological simulation in the framework of crystal-field Hamiltonian. The set of refined crystal-field parameters under the C2V site symmetry of the two ions satisfactorily produce good fits between calculated and experimentally observed energy-level structures, associated with the fine splitting of the luminescence lines in the 5D0→7FJ (J=0–4) transitions of the Eu(III) ion in [Eu(NTA)2·H2O]3− and in the 5D4→7FJ (J=6–0) transitions of the Tb(III) ion in [Tb(NTA)2·H2O]3−.

Polarized emission from KCl:Eu2+ single crystals

The polarization emission spectrum and the angular dependence of polarization ratio of the blue emission from KCl:Eu2+ were investigated at 78.8 K. The polarized emission at 420 nm consisted of several components. The angular dependence of polarization ratio of each component is proportional to sin(2 ) or -cos(2 ), when the exciting light is polarized at with respect to the z -axis for the [100]-[010] optical arrangement. The relaxed excited states (RESs) of Eu2+ responsible for the 420 nm emission are presented in terms of the adiabatic potential energy surface (APES), taking into account the Jahn-Teller effect (JTE) coupling to the Eg mode and the spin-orbit (SO) interaction. The charge-compensating cation vacancy (CCV, Vc - ) also causes an additive perturbation.

Luminescence of KCl single crystals doped with Ge atoms

The emission from KCl:Ge0 excited in the W range was measured as a function of the exciting photon energy and temperature. The polarized emission spectrum and the angular dependence of polarization ratio were also investigated. Like KCl:Bi3+, KCl:Ge0 single crystals produce two emission bands peaking at 345 and 395 nm. The interstitial Cl- ion is assumed to be responsible for the colour centre of the 345 and 395 nm emissions. The definitive assignment of these bands is presented in terms of the adiabatic potential energy surface, in which the Jahn-Teller effect is taken into account.

Luminescence of KCl:Bi3+ excited at the X absorption band

The emission from KCl:Bi3+ excited in the X absorption band (i.e. between the A and B absorption bands) was measured as a function of temperature. The polarized emission spectrum and the angular dependence of polarization ratio were also investigated. The X-band excitation produces two emission bands peaking at 345 and 395 nm, the centres of which are not the same. The loosely bonded Cl- ion arising from the substitution of Bi3+ ions into the KCl lattice is assumed to be the colour centre for the X-band emission. The definitive assignment of the two emission bands is presented in terms of the relaxed excited states of the perturbed Cl- ion, in which the Jahn-Teller interaction coupling to the B1 and B2 vibronic modes is taken into account.