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Table 1 Interaction energies including BSSE corrections (ΔE) of the seven 2TX...H2O complexes, BSSE, bond lengths of X--H (RX--H), hydrogen bond distances (rY...H), selected change of X--H bond lengths (ΔrX-H), stretching vibrational frequency of monomer upon complex formation (ΔνX-H), and the corresponding calculated change of infrared intensities (ΔIX-H) at the MP2/6-311G (d, p) level.

From: An ab initioand AIM investigation into the hydration of 2-thioxanthine

complexes ΔEa BSSEa X--H...Y R X-H b r Y ... H b ΔrX-Hb ΔνX-Hc ΔIX-Hd
I -7.6e 1.6e N(1)--H...Owg 1.027 1.919 +0.013 --230 +436
  (--6.6)f (0.6)f Ow--H...O(11)h 0.967 2.019 +0.009 --112 +134
II --12.7 1.9 N(7)--H...Ow 1.031 1.796 +0.020 --344 +642
  (--11.7) (0.6) Ow--H...O 0.971 1.912 +0.013 --194 +402
III --8.6 1.6 N(3)--H...Ow 1.024 1.924 +0.013 --216 +386
  (--6.8) (0.6) Ow--H...N 0.967 2.086 +0.009 --124 +158
IV --4.8 1.0 C--H...Ow 1.080 2.510 -0.001 +10 +19
  (--3.6) (0.4) Ow--H...N 0.964 2.129 +0.005 --73 +145
V --8.2 1.8 N(1)--H...Ow 1.031 1.838 +0.017 --313 +504
  (--7.0) (0.6) Ow--H...S 0.976 2.453 +0.018 --131 +152
VI --9.3 1.8 N(3)--H...Ow 1.037 1.800 +0.016 --366 +591
  (--8.2) (0.6) Ow--H...S 0.968 2.452 +0.010 --225 +436
VII --3.3 1.8 C--H...Ow 1.083 2.179 +0.002 --31 +133
  (--2.6) (0.4)       
  1. a kcal mol-1;b Å;ccm-1; d km mol-1; ecalculated at the MP2/6-311++G(2d, 2p)//MP2/6-311G(d, p) level; fcalculated at the B3LYP/6-311++G(2d,2p)//B3LYP/6-311G(d, p) level; gOw represents the oxygen atom of water.hchange in the O--H symmetrical stretch frequencies of water, the change in asymmetric stretch is small and not given here.