Transition metals excitation spectra

A supramolecular assembly of macromolecules bearing antenna dendron has been reported. Pyrazole-anchored PBE dendrons were synthesized to examine the coordination behavior to transition-metal cations (Cu, Au, Ag) [31]. Self-assembled metallacycles were found. The Cu-metallacycle further formed luminescent fibers about 1 pm in diameter. The luminescence (605 nm) occurred by the excitation of the dendron (280 nm) and the excitation spectrum was coincident with the absorption spectrum of the dendron, suggesting the antenna effect. Interestingly, the luminescence of the Cu-metallacycle fiber disappeared when the fiber was dissociated into the individual metallacycles in C2H2. 

A certain transition metal ion presents two optical absorption bands in a host crystal whose zero-phonon lines are at 600 nm and 700 nm, respectively. The former band has a Huang-Rhys parameter 5 = 4, while for the latter 5 = 0. Assuming coupling with a phonon of 300 cm for the two bands (a) display the 0 K absorption spectrum (absorption versus wavelength) for such a transition metal ion (b) display the emission spectra that you expect to obtain nnder excitation in both absorption bands and (c) explain how you expect these two bands to be affected by a temperature increase. 

Coulomb correlation energy, I/44, and thereby showed how the cationic and anionic energy levels were both equally important. These workers calculated the gap arising in the charge excitation spectrum of a single transition-metal impurity hybridizing with a... 

A principal obstacle to identification of defects is the difficulty of comparing the results from EPR, luminescence, absorption, and deep state experiments. Probably the least ambiguous is that between EPR and luminescence when, as for transition metal impurities, it is possible for optical Zeeman measurements of a sharp luminescence line to determine the ground state g factor. If the optical and EPR measurements give the same value, then the correlation is made (Watts, 1977). In some cases, when optical excitation enhances or quenches the EPR signal, there may be a similar response in the photoconductivity or luminescence excitation spectrum. 

Over the past 15 years there has been a wealth of research on development and application of transition metal complex sensitizers to the development of dye sensitized photoelectrochemical (solar) cells (DSSCs) [113]. Charge injection from the excited state of many sensitizers has been found to be on the subpicosecond timescale, and a key objective has been to identify chromophores that absorb throughout the visible spectrum. For this reason, Os(II) complexes appear attractive and a variety of attempts were made to make use of these complexes in DSSCs in the 1990s [114-116]. Work has continued in this area in recent years and representative examples are given below. 

Molecules in the second coordination sphere, that is, solvent or partners of an ion pair, can transfer charge to the metal ion of a coordination complex in an optically induced electronic transition. The excited states are, respectively, known as solvent to metal charge transfer (SMCT) and ion pair charge transfer (IPCT) excited states. A typical example are the ion pairs, [Cora(NH3)6]3 +, X-, formed between [Coln(NH3)6]3 + and halide and pseudohalide ions X. The UV-Vis spectrum of ion... 

Electronic Transitions In an electronic transition an electron is excited from an occupied to an empty molecular orbital (M.O.). The energy of such transitions normally corresponds to photons in the near IR, visible or UV region of the electromagnetic spectrum. Electronic absorption bands give rise to the colours of compounds, including ones without transition metals. 

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