Table 1.

Relevant geometric parameters (Å) describing the host-guest interactions. Tiiii(1) and Tiiii(2) cavitands form H-bonds with the α-ammonium group and with the side chain of the amino acid, respectively. The out of plane (oop) of the more inserted non-H atoms of the amino acid (or water molecule) is calculated with respect to the mean plane, defined by the four oxygen atoms of the cavitand P=O groups. A negative sign is used for atoms below the plane and inserted in the cavity of Tiiii. His(1) and His(2) correspond to the two crystallographic independent molecules of the dimeric 2 Tiiii[H, CH₃, CH₃]•His·2HCl complex. Values in brackets correspond to the II conformation of Arg.

Tiiii(1) H-Bonds	Arg	Lys	His(1)	His(2)
N–O2	2.71.	2.71.	2.81.	2.71.
N–O3	2.80	2.83	2.77	2.78
N–OW	2.74	2.72	2.64	2.66
OW–O1	2.90	2.87	2.76	2.81
OW–O4	2.83	2.90	2.73	2.87
oop N	0.70	0.55	0.89	0.89
oop Ow	−0.65	−0.86	0.36	0.13
Tiiii(2) H-Bonds	Arg	Lys	His(1)	His(2)
O1	Nη2 2.93 (2.70)	Nζ 2.84	Nδ1 2.70	Nδ1 2.69
O2	Nη1 2.92 (3.47)	Nζ 2.76
O3	Nε 2.76	Ow 2.68	Nε2 2.71	Nδ1 2.67
O4	Nη2 2.73 (3.45)	Ow 2.71
Ow		Nζ 2.72
oop	Nη1 −0.54 (−0.64)	Nζ 0.72	Cε1 −0.47	Cε1 −0.38
oop		Ow 0.29