Phosphaphenalenes are a class of
heterocyclic
A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). Heterocyclic organic chemistry is the branch of organic chemistry dealing with the synthesis, proper ...
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 ...
compounds containing
phosphorus
Phosphorus is a chemical element; it has Chemical symbol, symbol P and atomic number 15. All elemental forms of phosphorus are highly Reactivity (chemistry), reactive and are therefore never found in nature. They can nevertheless be prepared ar ...
with
molecular formula
A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as paren ...
. It is related to
phenalene , where one of its carbons is replaced by phosphorus (phenalene is a
polycyclic aromatic hydrocarbon
A Polycyclic aromatic hydrocarbon (PAH) is any member of a class of organic compounds that is composed of multiple fused aromatic rings. Most are produced by the incomplete combustion of organic matter— by engine exhaust fumes, tobacco, incine ...
).
Phosphaphenalene can exist in a number of
isomer
In chemistry, isomers are molecules or polyatomic ions with identical molecular formula – that is, the same number of atoms of each element (chemistry), element – but distinct arrangements of atoms in space. ''Isomerism'' refers to the exi ...
s depending on where in the ring system the phosphorus atom is placed. The phosphorus atom in these molecules has unusual properties, in particular changing its affinity as an electron acceptor when exposed to certain wavelengths of light. This makes phosphaphenalenes useful in optoelectronic applications such as temperature-dependent
luminescence
Luminescence is a spontaneous emission of radiation from an electronically or vibrationally excited species not in thermal equilibrium with its environment. A luminescent object emits ''cold light'' in contrast to incandescence, where an obje ...
and
electrochromism
Electrochromism is a phenomenon in which a material displays changes in color or Opacity (optics), opacity in response to an voltage, electrical stimulus.
In this way, a smart window made of an electrochromic material can block specific wavelen ...
(reversibly changes colour when electricity is applied).
References
Phosphorus heterocycles
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