Solvatochromism

In <a href="/facts/Chemistry/SrNqkGVm">chemistry</a>, solvatochromism is the phenomenon observed when the <a href="/facts/Color_of_chemicals/J5va4Cx5">colour</a> of a <a href="/facts/Solution_(chemistry)/MGchhMQV">solution</a> is different when the solute is <a href="/facts/Solvation/JVM6j8R1">dissolved</a> in different <a href="/facts/Solvent/LoMPMz8S">solvents</a>.

The solvatochromic effect is the way the spectrum of a substance (the solute) varies when the substance is dissolved in a variety of solvents. In this context, the <a href="/facts/Dielectric_constant/vnKbPTn1">dielectric constant</a> and <a href="/facts/Hydrogen_bonding/85V86IIg">hydrogen bonding</a> capacity are the most important properties of the solvent. With various solvents there is a different effect on the electronic <a href="/facts/Ground_state/ML7cfCug">ground state</a> and <a href="/facts/Excited_state/czcLYNnr">excited state</a> of the solute, so that the size of <a href="/facts/Energy_gap/VMvKsyna">energy gap</a> between them changes as the solvent changes. This is reflected in the <a href="/facts/Absorption_spectroscopy/GH7RC14D">absorption</a> or <a href="/facts/Emission_spectrum/fxumR717">emission spectrum</a> of the solute as differences in the position, intensity, and shape of the <a href="/facts/Spectral_bands/hw6CxHIS">spectroscopic bands</a>. When the spectroscopic band occurs in the <a href="/facts/Visible_spectrum/frPBh8o5">visible part</a> of the <a href="/facts/Electromagnetic_spectrum/24LARvFY">electromagnetic spectrum</a>, solvatochromism is observed as a change of <a href="/facts/Colour/XDvW7ESP">colour</a>. This is illustrated by <a href="/facts/Reichardt%27s_dye/vV9YY9dL">Reichardt's dye</a>, as shown in the image.
Negative solvatochromism corresponds to a <a href="/facts/Hypsochromic_shift/jcxBGf8A">hypsochromic shift</a> (or blue shift) with increasing solvent <a href="/facts/Chemical_polarity/KlIJ0zjB">polarity</a>. An examples of negative solvatochromism is provided by <a href="/facts/Brooker%27s_merocyanine/XhMdeMbS">4-(4′-hydroxystyryl)-N-methylpyridinium iodide</a>, which is red in <a href="/facts/1-propanol/NoSmhEhh">1-propanol</a>, orange in <a href="/facts/Methanol/EIfpoNCg">methanol</a>, and yellow in <a href="/facts/Water/0lkXnJPK">water</a>.
Positive solvatochromism corresponds to a <a href="/facts/Bathochromic_shift/Y4Pb1tvp">bathochromic shift</a> (or red shift) with increasing solvent polarity. An example of positive solvatochromism is provided by <a href="/facts/Michler%27s_ketone/Y0SWW3Jn">4,4'-bis(dimethylamino)fuchsone</a>, which is orange in <a href="/facts/Toluene/Pzdt8dwD">toluene</a>, red in <a href="/facts/Acetone/cVyJxKqw">acetone</a>.
The main value of the concept of solvatochromism is the context it provides to predict colors of solutions. Solvatochromism can in principle be used in <a href="/facts/Sensor/RN8SXbjs">sensors</a> and in <a href="/facts/Molecular_electronics/nC056GHG">molecular electronics</a> for construction of <a href="/facts/Molecular_switch/qVl74cKW">molecular switches</a>. Solvatochromic dyes are used to measure solvent parameters, which can be used to explain solubility phenomena and predict suitable solvents for particular uses.
Solvatochromism of the <a href="/facts/Photoluminescence/L1u2PJIa">photoluminescence</a>/<a href="/facts/Fluorescence/qsJVT2qP">fluorescence</a> of <a href="/facts/Carbon_nanotubes/atuDPPaG">carbon nanotubes</a> has been identified and used for optical sensor applications. In one such application, the <a href="/facts/Wavelength/kcJU0ymz">wavelength</a> of the fluorescence of peptide-coated carbon nanotubes was found to change when exposed to <a href="/facts/Explosive/sUme5Pp8">explosives</a>, facilitating detection. However, more recently the small chromophore solvatochromism hypothesis has been challenged for carbon nanotubes in light of older and newer data showing <a href="/facts/Electrochromism/FRcyVXKv">electrochromic</a> behavior. These and other observations regarding non-linear processes on the semiconducting nanotube suggest colloidal models will require new interpretations that are in line with classic semiconductor optical processes, including electrochemical processes, rather than small molecule physical descriptions. Conflicting hypotheses may be due to the fact the nanotube is only a single atom thick material interface unlike other "bulk" nanomaterials.

Solvatochromism open-in-new

Solvatochromism