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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. Charge-transfer complex - Wikipedia

    en.wikipedia.org/wiki/Charge-transfer_complex

    In chemistry, charge-transfer (CT) complex, or electron donor-acceptor complex, describes a type of supramolecular assembly of two or more molecules or ions. The assembly consists of two molecules that self-attract through electrostatic forces, i.e., one has at least partial negative charge and the partner has partial positive charge, referred ...

  4. 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?

  5. 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.

  6. 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]

  7. 18-electron rule - Wikipedia

    en.wikipedia.org/wiki/18-electron_rule

    Compounds that obey the 18-electron rule are typically "exchange inert". Examples include [Co(NH 3) 6]Cl 3, Mo(CO) 6, and [Fe(CN) 6] 4−.In such cases, in general ligand exchange occurs via dissociative substitution mechanisms, wherein the rate of reaction is determined by the rate of dissociation of a ligand.

  8. Ring expansion and contraction - Wikipedia

    en.wikipedia.org/wiki/Ring_expansion_and_contraction

    The specific problem is: uneven quality of sourcing—substantially primary (and not full) sources—reflecting editorial decisions to include/exclude examples, decisions that, i, constitute original research, and ii, that are unfortunately not scholarly and up to date. Please help improve this article if you can.

  9. 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.