PIDA, or poly(diiododiacetylene), is an

organic polymer A polymer () is a substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeating subunits derived from one or more species of monomers. Due to their broad spectrum of properties, bot ...

that has a

polydiacetylene Polydiacetylenes (PDAs) are a family of conducting polymers closely related to polyacetylene. They are created by the 1,4 topochemical polymerization of diacetylenes. They have multiple applications from the development of organic films to immobili ...

backbone. It is one of the simplest polydiacetylenes that has been synthesized, having only

iodine Iodine is a chemical element; it has symbol I and atomic number 53. The heaviest of the stable halogens, it exists at standard conditions as a semi-lustrous, non-metallic solid that melts to form a deep violet liquid at , and boils to a vi ...

atoms as side chains. It is created by 1,4 topochemical

polymerization In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many fo ...

of diiodobutadiyne. It has many implications in the field of polymer chemistry as it can be viewed as a precursor to other polydiacetylenes by replacing iodine atoms with other side chains using

organic synthesis Organic synthesis is a branch of chemical synthesis concerned with the construction of organic compounds. Organic compounds are molecules consisting of combinations of covalently-linked hydrogen, carbon, oxygen, and nitrogen atoms. Within the gen ...

, or as an iodinated form of the carbon allotrope

carbyne In organic chemistry, a carbyne is a general term for any compound whose structure consists of an electrically neutral carbon atom connected by a single covalent bond and has three non-bonded electrons. The carbon atom has either one or three ...

Structure

The backbone of PIDA is highly conjugated and allows for the formation of an extended pi system along the length of the polymer. This property of PIDA allows it to transport electricity and act as a molecular wire or an organic semiconductor. Considering PIDA's backbone and the fact that Iodine atoms can easily undergo elimination, it is conceivable that PIDA can be subjected to full reductive deiodination in the presence of a Lewis base, such as

pyrrolidine Pyrrolidine, also known as tetrahydropyrrole, is an organic compound with the molecular formula (CH2)4NH. It is a cyclic secondary amine, also classified as a saturated heterocycle. It is a colourless liquid that is miscible with water and most ...

to yield carbyne.

Synthesis

PIDA is synthesized from diiodobutadiyne via 1,4 topochemical polymerization. In order to meet the geometric requirements for polymerization, a host–guest strategy is used by combining a host molecule and diiodobutadiyne in solution and allowing co-crystallization to occur. This can be utilized because hosts that are most commonly used are able to bond to the diyne monomer by

halogen bond In chemistry, a halogen bond (XB or HaB) occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecul ...

ing from the lewis acidic iodine atom to a lewis basic nitrogen of the host (usually a nitrile or pyridine). In order to give a proper repeat distance to the monomers (5 Å), the hosts also contain oxalamide groups that create a hydrogen bonding network throughout the crystal. In most instances, polymerization is spontaneous upon crystallization or exposure to UV radiation/pressure.

Reactions

PIDA Can undergo carbonization at high temperatures near 900 °C and reductive dehalogenation carbonization when exposed to pyrrolidine at room temperature. Attempts have been made to replace iodine side groups with other functional groups. There are also attempts being made at making other halogen analogs of PIDA.

References

{{reflist Conductive polymers Organic polymers Organoiodides Alkyne derivatives

Structure

Synthesis

Reactions

See also

References