Advanced level inorganic chemistry: UV and visible light absorption spectroscopy of titanium compounds

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Doc Brown's Advanced Chemistry: PART 15.5 uv and visible absorption spectra of titanium complex ions - transition metal absorption spectroscopy - titanium compounds

Doc Brown's Chemistry Advanced Level Pre-University Chemistry Revision Study Notes for UK IB KS5 A/AS GCE advanced A level organic chemistry students US K12 grade 11 grade 12 organic chemistry courses Spectroscopic methods of analysis and molecular structure determination investigating titanium complexes

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15.5.1 The origin of colour, the wavelengths of visible light, our perception!

15.5.2 uv-visible spectroscopy theory, spectrometer, examples of absorption & reflectance spectra explained

15.5.3 uv-visible absorption spectra - index of examples: uses, applications, more on the chemistry of colour

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The uv-visible absorption spectra of some titanium complex ions and compounds

uv-visible absorption spectrum of the hexaaquatitanium(III) transition metal complex ion explaining colour of Ti3+ ion

structure shape of the hexaaquatitanium(III) ion, [Ti(H2O)6]3+(aq) octahedral purple colour of Ti3+ ionThe uv-visible absorption spectrum for the hexaaquatitanium(III) ion, [Ti(H2O)6]3+(aq), shows a λmax of ~520 nm, with strong absorption in the blue-green-yellow region, but little absorption in the violet and red regions, resulting in the ion being a purple in aqueous solution from a combination of violet and red (often quoted as violet in colour).

Note the strong absorption in the 'invisible' ultraviolet region <380 nm).

electronic energy level diagram for the titanium(III) ion hexaaqatitanium(III) complex Ti3+ 3d orbital field splitting diagram

The electronic level field splitting diagram above shows the promotion of an electron by a visible light photon from the 3d ground state to the upper level of the 3d orbitals.

For more details see The chemistry of titanium

 

electronic energy level diagram for the titanium(III) ion hexaaqatitanium(II) complex Ti2+ 3d orbital field splitting diagram

structure shape of the hexaaquatitanium(II) ion, [Ti(H2O)6]2+(aq) octahedral violet colour of the Ti2+ ionA solution of the hexaaquatitanium(II) ion, [Ti(H2O)6]2+(aq) is violet.

(I couldn't find a uv-visible absorption spectrum for the hexaaquatitanium(II)

The electronic situation is slightly different than the hexaaquatitanium(III) ion, [Ti(H2O)6]3+(aq) ion, giving a different  ∆Eelec, but visible light photons still provide the necessary excitation energy.

 

electronic energy level diagram for the titanium(IV) compounds field 3d orbital splitting diagram tetrahedral complex

Two electronic diagrams showing why most titanium(IV) ions or compounds are colourless in solution or a white solid.

There are no electrons in the theoretical Ti4+ ion, that can be promoted from a lower to a higher in the 3d orbitals.

electronic energy level diagram for the titanium(IV) compounds field 3d orbital splitting diagram octahedral complex

As a result, titanium(IV) oxide, TiO2 (titanium dioxide), is a white solid from the reflectance of most visible light photons.

Titanium(IV) chloride,TiCl4, is a colourless covalent liquid, tetrahedral in shape - four chloride ions effectively acts a four electron pair donating ligands.

Hydrated TiO2 dissolves in conc. hydrofluoric acid to give a colourless solution of the hexafluorotitanate(IV) ion, an octahedral shaped complex with the formula [TiF6]2-(aq).

The hexachlorotitanate(IV) ion, is another octahedral shaped complex with the formula [TiCl6]2-(aq) also exists, but is apparently pale yellow.

For more details see The chemistry of titanium


Key words & phrases: interpreting the uv-visible absorption spectra of aqueous titanium(III) ion, identifying the maximum absorption peaks in the uv-visible absorption spectra of aqueous titanium(III) ion, explaining the uv-visible absorption spectra of aqueous titanium(III) ion, how to use the visible absorption spectra of aqueous titanium(III) ion to explain the different colours of aqueous titanium(III) ion, applications of the uv-visible absorption spectra of aqueous titanium(III) ion interpreting the uv-visible absorption spectrum of aqueous titanium(III) ion, identifying the maximum absorption peaks in the uv-visible absorption spectrum of aqueous titanium(III) ion, explaining the uv-visible absorption spectrum of aqueous titanium(III) ion, how to use the visible absorption spectra of aqueous titanium(III) ion to explain the colour of aqueous titanium(III) ion, applications of the uv-visible absorption spectrum of aqueous titanium(III) ion


Associated links

The chemistry of titanium

Index of Advanced A level Notes on the 3d block and Transition Metals

GCSE/IGCSE revision notes on Transition Metals

UV and visible spectroscopy index

General introduction to electron configuration of transition metal ions and colour theory

SPECTROSCOPY INDEXES

All Advanced Inorganic Chemistry Notes

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