Arne Zilian

Hole-burning and resonant luminescence line-narrowing of [Rh(phpy)2bpy]+ in glassy matrices

Abstract Persistent hole-burning of the triplet ligand-centred state in [Rh(phpy) 2 bpy] + in organic glasses is reported. In the scanning range of ± 3.8 GHz, no sideholes could be detected. From luminescence-line-narrowing and hole-burning experiments in moderate external magnetic fields of up to 0.83 T, it is concluded that the zero-field splitting is in the range of 9 ± 3 GHz but not correlated. At 4.2 K, the components of the triplet state are not thermalised, even in a field of 0.83 T. Homogeneous linewidths of 0.35 GHz and 0.8 GHz are deduced for the glycerol glass at 2.1 K and the ethanol:methanol 4:1 (v/v) glass at 1.6 K, respectively.

High-resolution laser spectroscopy of cyclometalated Rh (III)-thienylpyridine complexes

Abstract The cyclometalated rhodium(III) complexes [Rh(thpy)2L]+ with L=bpy, en or [μ-Cl2-(thpy)2Rh]− are studied in poly(methylmethacrylate) (PMMA) or in mixed crystals of the corresponding [Rh(phpy)2L]+ complexes. High-resolution luminescence and excitation spectra of the complexes at temperatures around 5 K are presented. The vibrational sidebands are fully resolved and allow us to compare the vibrational structure of the ground and lowest excited state. All thpy− complexes show nearly identical vibrational sidebands. The possibilities to obtain an estimate of excited state geometries are discussed.

Zeeman spectra of a rhodium(III) tris chelate complex

Excitation and luminescence line narrowing techniques at temperatures between 1.5 and 5 K are used to study the lowest triplet states of the cyclometalated Rh(III) complex [Rh(thpy)2(bpy)]+ (thpyH = 2-thienylpyridine; bpy = 2,2′-bipyridine) doped into a crystalline host and a glass. Crystal excitation spectra reveal two origins C and D separated by 156 cm-1. Their zero field splitting is shown to be less than 1 cm-1. Zeeman spectra of the narrowed excitation and luminescence origin C show an isotropic splitting into 5 lines, and their energy separation depends linearly on the applied field. The 5 lines are a superposition of spectra from three sets of triplets characterized by ms = +1, 0, -1 and a g-factor 2.0±0.1. Using the line intensities, the spin-lattice relaxation rate within the triplet at 4.2 K is estimated to be 160 and 6400 s-1 for fields of 2 and 4 T, respectively.

Excitation localization in mixed rhodium-chelates

Abstract Optically detected magnetic resonance experiments have been performed for photo-excited [Rh(thpy) 2 (bpy)] + doped in a single crystal of [Rh(phpy) 2 (bpy)]PF 6 . The results provide unambiguous evidence for a photo-induced triplet state excitation, localized on one of the thienylpyridyl anions chelated to Rh 3+ . The zero-field splitting parameters of the thienylpyridyl anion in the phosphorescent triplet state were determined to be | D | = 3445 MHz and | E | = 865 MHz.

Luminescence line narrowing in coordination compounds : tris chelate complexes of rhodium(III)

Abstract The nature of the first excited states in several tris chelate complexes of Rh3+ is elucidated by luminescence line narrowing (LLN). The technique is very effective in glassy matrices at temperatures up to 40 K. The dependences on the matrix and on the chemical composition of the complexes are studied. A four-level pattern of emitting states, as derived from high-resolution crystal spectra, accounts for the effects observed in the LLN spectra.

High-resolution spectroscopy of cyclometalated rh(iii) complexes

Abstract Optical spectroscopic properties of Rh(III) complexes with the cyclometalating ligands 2-phenylpyridine and 2-thienylpyridine are discussed. Using mixed crystals high-resolution spectra are obtained. They allow us to determine the vibrational structure in both the lowest excited states and the ground state. Zeeman spectra of the origin lines reveal that i) the field dependent splitting is isotropic and has a g-value of 2.0 + 0.1 and ii) the zero field splitting is smaller than 0.4 cm −1 . The spin-lattice relaxation rate constant depends quadratically on the applied field strength and equals the luminescence decay rate constant at 4.2 K in a field of 2.5 T.

Luminescence of Rh(III) chelate complexes: Line narrowing and the influence of host and temperature

Abstract The luminescence line narrowing technique is applied to the cyclometalated complexes [Rh(thpy) 2 bpy] + , [Rh(thpy) 2 en] + and [Rh(phpy) 2 bpy] + (thpyH = 2-(2-thienyl)pyridine, bpy = 2,2′-bipyridine, en = ethylenediamine and phpyH = 2-phenylpyridine). The dependence on temperature and the influence of different hosts are studied.

Absorption and emission spectra of tris(2,3-diamino-2,3-dimethylbutane) chromium(III)

Abstract The chromium(III) complex with the chelating diamine 2,3-diamino-2,3-dimethylbutane (tmen) is prepared by prolonged refluxing of anhydrous CrCl 3 with tmen in tetrahydrofurane. Compared to the parent Cr(en) 3 3+ species the absorption bands of the novel Cr(tmen) 3 3+ are red shifted and more intense with maxima at 376 and 504 nm and extinction coefficients of 140 and 154 M −1 cm −1 , respectively. A third, very weak absorption (ϵ ∼ 1 M −1 cm −1 ) is observed at 684 nm. The low temperature luminescence is attributed to a 2 E → 4 A 2 transition and is counterion dependent: chloride, nitrate and triflate salts exhibit a rather broad emission; the sulfate, tetrafluoroborate and the Cr(III) doped Rh(tmen) 3 - (BF 4 ) 3 show a well resolved series of very narrow signals.