chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules a ...

, phi bonds (φ bonds) are usually

covalent A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atom ...

chemical bond A chemical bond is the association of atoms or ions to form molecules, crystals, and other structures. The bond may result from the electrostatic force between oppositely charged ions as in ionic bonds or through the sharing of electrons a ...

s, where six lobes of one involved

atomic orbital In quantum mechanics, an atomic orbital () is a Function (mathematics), function describing the location and Matter wave, wave-like behavior of an electron in an atom. This function describes an electron's Charge density, charge distribution a ...

overlap Overlap may refer to: * In set theory, an overlap of elements shared between sets is called an intersection, as in a Venn diagram. * In music theory, overlap is a synonym for reinterpretation of a chord at the boundary of two musical phrases * Ove ...

six lobes of the other involved atomic orbital. This overlap leads to the formation of a bonding

molecular orbital In chemistry, a molecular orbital is a mathematical function describing the location and wave-like behavior of an electron in a molecule. This function can be used to calculate chemical and physical properties such as the probability of finding ...

with three nodal planes which contain the internuclear axis and go through both atoms. The Greek letter φ in their name refers to f orbitals, since the

orbital symmetry In chemistry, molecular symmetry describes the symmetry present in molecules and the classification of these molecules according to their symmetry. Molecular symmetry is a fundamental concept in chemistry, as it can be used to predict or explai ...

of the φ bond is the same as that of the usual (6-lobed) type of f orbital when seen down the bond axis. There was one possible candidate reported in 2005 of a molecule with phi bonding: a U−U bond in the molecule diuranium (U₂). However, later studies that accounted for

spin–orbit interaction In quantum mechanics, the spin–orbit interaction (also called spin–orbit effect or spin–orbit coupling) is a relativistic interaction of a particle's spin with its motion inside a potential. A key example of this phenomenon is the spin– ...

s found that the bonding was only of fourth order. Experimental evidence for phi bonding between a

thorium Thorium is a chemical element; it has symbol Th and atomic number 90. Thorium is a weakly radioactive light silver metal which tarnishes olive grey when it is exposed to air, forming thorium dioxide; it is moderately soft, malleable, and ha ...

atom and

cyclooctatetraene 1,3,5,7-Cyclooctatetraene (COT) is an unsaturated derivative of cyclooctane, with the formula C8H8. It is also known as nnulene. This polyunsaturated hydrocarbon is a colorless to light yellow flammable liquid at room temperature. Because of ...

in thorocene has been supported by computational analysis, though this mixed-orbital bond has strong ionic character and is not a traditional phi bond.

References

{{Chemical bonding theory Chemical bonding Hypotheses in chemistry