organic chemistry Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic matter, organic materials, i.e., matter in its various forms that contain ...

, a fulgide is any of a class of

photochromic Photochromism is the reversible change of color upon exposure to light. It is a transformation of a chemical species (photoswitch) between two forms through the absorption of electromagnetic radiation (photoisomerization), where each form has a d ...

compounds consisting of a bis methylene-

succinic anhydride Succinic anhydride, is an organic compound with the molecular formula (CH2CO)2O. This colorless solid is the acid anhydride of succinic acid. Preparation In the laboratory, this material can be prepared by dehydration of succinic acid. Such dehy ...

core that has an

aromatic In organic chemistry, aromaticity is a chemical property describing the way in which a conjugated system, conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibits a stabilization stronger than would be expected from conjugati ...

group as a

substituent In organic chemistry, a substituent is one or a group of atoms that replaces (one or more) atoms, thereby becoming a moiety in the resultant (new) molecule. The suffix ''-yl'' is used when naming organic compounds that contain a single bond r ...

. The highly conjugated system is a good

chromophore A chromophore is the part of a molecule responsible for its color. The word is derived . The color that is seen by our eyes is that of the light not Absorption (electromagnetic radiation), absorbed by the reflecting object within a certain wavele ...

. It can undergo reversible

photoisomerization In chemistry, photoisomerization is a form of isomerization induced by photoexcitation. Both reversible and irreversible photoisomerizations are known for photoswitchable compounds. The term "photoisomerization" usually, however, refers to a rev ...

induced by

ultraviolet light Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of th ...

, converting between the ''E'' and ''Z'' isomers, both of which are typically colorless compounds. Unlike the more-stable ''Z'' isomer, the ''E'' isomer can also undergo a photochemically-induced electrocyclic reaction, forming a new ring and becoming a distinctly colored product called the ''C'' form. It is thus the two-step ''Z''–''C'' isomerization that is the photochromic change starting from the stable uncyclized form. : Fulgide isomerization

History

The first compound of this class was synthesized in 1906 (by , using the Stobbe condensation), with the name based on the Latin word '' fulgere'', meaning "to shine", for the shiny and large variety of colors of the

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...

. The photochromic mechanism of fulgide was reported in 1968. It was not until 1981 that derivatives of fulgide, which made thermally stable

, was reported. By editing both non-aromatic substituents and aromatic substituent, fulgide derivatives that are high in

thermal stability In thermodynamics, thermal stability describes the stability of a water body and its resistance to mixing.Schmidt, W. 1928. Über Temperatur und Stabilitätsverhältnisse von Seen. Geogr. Ann 10: 145 - 177. It is the amount of work needed to tra ...

and photostability were synthesized.

Derivatives

Various other

carbonyl In organic chemistry, a carbonyl group is a functional group with the formula , composed of a carbon atom double bond, double-bonded to an oxygen atom, and it is divalent at the C atom. It is common to several classes of organic compounds (such a ...

structures have been studied, in addition to the original succinic anhydride. The goals includ controlling various chemical properties, photochemical properties, and embedding of this structural motif in more complex molecules.

Fulgimide

Fulgimide is an analog that has

succinimide Succinimide is an organic compound with the formula (CH2)2(CO)2NH. This white solid is used in a variety of organic syntheses, as well as in some industrial silver plating processes. The compound is classified as a cyclic imide. It may be prepared ...

instead of succinic anhydride. It has nearly the same photochromic properties, but the

imide In organic chemistry, an imide is a functional group consisting of two acyl groups bound to nitrogen. The compounds are structurally related to acid anhydrides, although imides are more resistant to hydrolysis. In terms of commercial applications ...

is substantially more stable than the

carboxylic acid anhydride An organic acid anhydride is an acid anhydride that is also an organic compound. An acid anhydride is a compound that has two acyl groups chemical bond, bonded to the same oxygen atom. A common type of organic acid anhydride is a carboxylic anhyd ...

towards

hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...

. It also involves a less-complicated synthetic process for attaching substituents onto the structural core. The nitrogen atom provides a point of attachment for chains that can be

cross-link In chemistry and biology, a cross-link is a bond or a short sequence of bonds that links one polymer chain to another. These links may take the form of covalent bonds or ionic bonds and the polymers can be either synthetic polymers or natural ...

ed to form

polymer A polymer () is a chemical substance, substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeat unit, repeating subunits derived from one or more species of monomers. Due to their br ...

Fulgenolide

Fulgenolide is a

lactone Lactones are cyclic carboxylic esters. They are derived from the corresponding hydroxycarboxylic acids by esterification. They can be saturated or unsaturated. Lactones are formed by lactonization, the intramolecular esterification of the corresp ...

analog: one of the two succinic anhydride

carbonyl group In organic chemistry, a carbonyl group is a functional group with the formula , composed of a carbon atom double-bonded to an oxygen atom, and it is divalent at the C atom. It is common to several classes of organic compounds (such as aldehydes ...

s is replaced by an

alkyl In organic chemistry, an alkyl group is an alkane missing one hydrogen. The term ''alkyl'' is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula of . A cycloalkyl group is derived from a cy ...

link. Fulgenolides have a larger

quantum yield In particle physics, the quantum yield (denoted ) of a radiation-induced process is the number of times a specific event occurs per photon absorbed by the system. \Phi(\lambda)=\frac Applications Fluorescence spectroscopy The fluorescence ...

than other fulgide derivative and has a λ_max of the ''C'' form in near IR-region.

Fulgenate

Fulgenate is a di

ester In chemistry, an ester is a compound derived from an acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds contain a distin ...

analog. However, fulgenates do not have photochromic characteristics.

References

{{reflist Oxygen heterocycles Carboxylic anhydrides Heterocyclic compounds with 1 ring Five-membered rings