Ab initio MP2/aug'-cc-pVTZ calculations have been carried out to investigate the pnicogen-bonded complexes F 4-n H n P + :N-base, for n = 1-4, each with a linear or nearly linear H ax -P···N alignment. The sp 3 -hybridised nitrogen bases include NH 3 , NClH 2 , NFH 2 , NCl 2 H, NCl 3 , NFCl 2 , NF 2 H, NF 2 Cl, and NF 3, and the sp bases are NCNH 2 , NCCH 3 , NP, NCOH, NCCl, NCH, NCF, NCCN, and N 2 . Binding energies increase as the P-N distance decreases, with an exponential curve showing this relationship when complexes with sp 3 and sp hybridised bases are treated separately. However, the correlations are not as good as they are for the complexes F 4-n H n P + :N-base for n = 0-3 with F-P···N linear. Different patterns are observed for the change in the binding energies of complexes with a particular base as the number of F atoms in the acid changes. Thus, the particular acid-base pair is a factor in determining the binding energies of these complexes. Three different charge-transfer interactions stabilise these complexes, namely N lp →σ * P-H ax , N lp →σ * P-F eq , and N lp →σ * P-H eq . Unlike the corresponding complexes with F-P···N linear, N lp →σ * P-H ax is not always the dominant charge-transfer interaction, since N lp →σ * P-F eq is greater in some complexes. N lp →σ * P-H eq makes the smallest contribution to the total charge-transfer energy. The total charge-transfer energies of all complexes increase exponentially as the P-N distance decreases in a manner very similar to that observed for the series of complexes with F-P···N linear. Equation-of-motion coupled cluster singles and doubles (EOM-CCSD) spin-spin coupling constants 1p J(P-N) across the pnicogen bond vary with the P-N distance, but different patterns are observed which depend on the nature of the acid, and for some acids, on the hybridisation of the nitrogen base. 1p J(P-N) values for complexes of F 3 HP + initially increase as the P-N distance decreases, reach a maximum, and then decrease with decreasing P-N distance as the P···N bond acquires increased covalent character. 1p J(P-N) for complexes with H-P···N linear and those with F-P···N linear exhibit similar distance dependencies depending on the number of F atoms in equatorial positions and the hybridisation of the base. Complexation may increase, decrease, or leave the P-H ax distance unchanged, but 1 J(P-H ax ) always decreases relative to the corresponding isolated ion. Decreasing 1 J(P-H ax ) can be related to decreasing intermolecular P-N distance.