¹⁵N‐, ¹H‐, and ¹³C‐NMR chemical shifts and electronic properties of aromatic diamines and dianhydrides

<jats:title>Abstract</jats:title><jats:p>We measured the <jats:sup>15</jats:sup>N‐, <jats:sup>1</jats:sup>H‐, and <jats:sup>13</jats:sup>C‐NMR chemical shifts for a series of aromatic diamines and aromatic tetracarboxylic dianhydrides dissolved in DMSO‐<jats:italic>d</jats:italic><jats:sub>6</jats:sub>, and discuss the relationships between these chemical shifts and the rate constants of acylation (<jats:italic>k</jats:italic>) as well as such electronic‐property‐related parameters such as ionization potential (IP), electronic affinity (EA), and the energy ε of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). The <jats:sup>15</jats:sup>N chemical shifts of the amino group of diamines (δ<jats:sub>N</jats:sub>) depend monotonically on the logarithm of <jats:italic>k</jats:italic> (log <jats:italic>k</jats:italic>) and on IP. We inferred the reactivities of diamines whose acylation rates have not been measured from their δ<jats:sub>N</jats:sub>, and we propose an arrangement of diamines in the order of their reactivity. The <jats:sup>1</jats:sup>H chemical shift of amino hydrogens (δ<jats:sub>H</jats:sub>) and the <jats:sup>13</jats:sup>C chemical shift of carbons bonded to nitrogen (δ<jats:sub>C</jats:sub>) are roughly proportional to δ<jats:sub>N</jats:sub>, but these shifts are not as closely correlated with log <jats:italic>k</jats:italic> and IP. Although the <jats:sup>13</jats:sup>C chemical shifts of the carbonyl carbon of dianhydrides (δ<jats:sub>C</jats:sub>,) varies much less than the δ<jats:sub>C</jats:sub> and δ<jats:sub>N</jats:sub> of diamines, δ<jats:sub>C</jats:sub>, can be an index of acylation reactivity for dianhydrides because it is closely correlated with ε<jats:sub>LUMO</jats:sub>. These facts indicate that the chemical shifts of diamines and dianhydrides are displaced according to their electron‐donor and electron‐acceptor properties, and that these chemical shifts can be used as indices of the electronic properties of monomers. Changes in reactivity caused by the introduction of trifluoromethyl groups into diamines and dianhydrides are inferred from the displacements of δ<jats:sub>N</jats:sub> and δ<jats:sub>C</jats:sub> © 1992 John Wiley & Sons, Inc.</jats:p>