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  2. Charge-transfer band - Wikipedia

    en.wikipedia.org/wiki/Charge-transfer_band

    Absorption spectrum of an aqueous solution of potassium permanganate, showing a vibronic fine structure in the LMCT band. The tetraoxides of d 0 metal centers are often deeply colored for the first row metals. This coloration is assigned to LMCT, involving transfer of nonbonding electrons on the oxo ligands to empty d-levels on the metal.

  3. List of unsolved problems in chemistry - Wikipedia

    en.wikipedia.org/wiki/List_of_unsolved_problems...

    RNA folding problem: Is it possible to accurately predict the secondary, tertiary and quaternary structure of a polyribonucleic acid sequence based on its sequence and environment? Protein design : Is it possible to design highly active enzymes de novo for any desired reaction?

  4. Molybdate - Wikipedia

    en.wikipedia.org/wiki/Molybdate

    In chemistry, a molybdate is a compound containing an oxyanion with molybdenum in its highest oxidation state of +6: O − −Mo(=O) 2 −O −. Molybdenum can form a very large range of such oxyanions , which can be discrete structures or polymeric extended structures, although the latter are only found in the solid state.

  5. Charge-transfer complex - Wikipedia

    en.wikipedia.org/wiki/Charge-transfer_complex

    A well-known example is the complex formed by iodine when combined with starch, which exhibits an intense purple charge-transfer band. This has widespread use as a rough screen for counterfeit currency. Unlike most paper, the paper used in US currency is not sized with starch. Thus, formation of this purple color on application of an iodine ...

  6. Transition metal - Wikipedia

    en.wikipedia.org/wiki/Transition_metal

    For example, the colour of chromate, dichromate and permanganate ions is due to LMCT transitions. Another example is that mercuric iodide , HgI 2 , is red because of a LMCT transition. A metal-to-ligand charge transfer (MLCT) transition will be most likely when the metal is in a low oxidation state and the ligand is easily reduced.

  7. Vibronic spectroscopy - Wikipedia

    en.wikipedia.org/wiki/Vibronic_spectroscopy

    As an example from inorganic chemistry the permanganate ion, MnO − 4, in aqueous solution has an intense purple colour due to an O → Mn ligand-to-metal charge transfer band (LMCT) in much of the visible region. [22] This band shows a progression in the symmetric Mn–O stretching vibration. [23]

  8. Ring expansion and contraction - Wikipedia

    en.wikipedia.org/wiki/Ring_expansion_and_contraction

    Ring opening as a means of ring expansion can also be applied to larger systems to give access to even larger ring syscyclization. The Grob fragmentation can be applied as an example of such an expansion. Like the pinacol type migration the Grob fragmentation relies on an electron donating group to promote the bond migration and encourage the ...

  9. Hexaamminecobalt(III) chloride - Wikipedia

    en.wikipedia.org/wiki/Hexaamminecobalt(III)_chloride

    Hexaamminecobalt(III) chloride is the chemical compound with the formula [Co(NH 3) 6]Cl 3.It is the chloride salt of the coordination complex [Co(NH 3) 6] 3+, which is considered an archetypal "Werner complex", named after the pioneer of coordination chemistry, Alfred Werner.