For the AB molecule, the energy is given as a function of bond distance, r:

Typically the bond distance to the apical ligands is longer than to the equatorial ligands.

Bond strength (energy) can be directly related to the bond length/bond distance.

J-coupling contains information about bond distance and angles.

X-ray crystallography is used to measure the bond distances between the metal and the ligands, which give insight into the spin state of the complex.

For example, the Mt-O bond distance is expected to be around 1.9 Å.

The bond distance was measured to be 2.973(4) Å.

In order to get the most orbital overlap the bond distances are much shorter than expected.

In a bond between two identical atoms half the bond distance is equal to the covalent radius.

The bond distance has been measured at 1.8934 Å.