Chemistry and Crystal Structures of Complexes of Caffeine and Tea Catechin - Caffeine: Chemistry, Analysis, Function and Effects - page 58

d n 0 t 2 n g | 3

Figure 4.5 Intermolecular interactions of the 1 : 1 complex of caffeine and CA, and

CA alone. (a) 1 : 1 complex of caffeine and CA. Black and gray dotted-
lines indicate O-H...O and O-H...N hydrogen bonds, respectively. (b) CA
alone. Black arrow indicates CH-p interaction.

Table 4.2 Hydrogen bonds in 1 : 1 complex of caffeine and CA.

D-H A D…A D-H H…A /D-H…A
OH(2O) a O(1) 2.823(6) 0.83 2.00 172.69
OH(3O) O(9) 2.672(7) 0.84 1.84 167.73
OH(6O) N(3) 2.770(7) 0.82 1.98 161.96
OH(9O) O(8) 2.727(6) 0.82 1.93 163.65
a Atom label in ORTEP drawing. D, H and A indicate hydrogen-bonding donor, hydrogen atom
and hydrogen-bonding acceptor, respectively. A unit of length is s.

Table 4.3 Hydrogen bonds in CA alone.

D-H A D…A D-H H…A /D-H…A
OH(2O) a O(1) 2.801(5) 0.84 1.97 169.74
OH(3O) O(8) 2.762(7) 0.84 1.93 171.84
OH(5O) O(4) 2.684(7) 0.84 1.90 153.77
OH(6O) O(7) 2.685(7) 0.84 1.87 162.53
OH(7O) O(2) 2.856(8) 0.84 2.04 163.82
a Atom label in ORTEP drawing. D, H and A indicate hydrogen-bonding donor, hydrogen atom
and hydrogen-bonding acceptor, respectively. A unit of length is s.