Non-covalent synthesis of ionic and molecular complexes of benzoic acid and substituted 2-aminopyrimidines by varying aryl/alkyl substituents and their supramolecular chemistry

Abstract

The non-covalent synthesis of ionic and molecular complexes of substituted 2-aminopyrimidines with benzoic acid in crystalline solid phase is reported. The nature of supramolecular architecture varied with the substituents in the 2-aminopyrimidine ring. Two complexes have been synthesised from two differently substituted 2-aminopyrimidines and benzoic acid. In one case, proton transfer takes place and an ionic organic salt is formed, whereas in the other, there is no proton transfer and a hydrogen-bonded molecular complex is formed.

Keywords:

• Molecular recognition
• Supramolecular chemistry
• Crystal engineering
• Host-guest

Acknowledgements

SPG, SJ and AH acknowledge the DST [SR/S1/OC-13/2005] and CSIR [01(1913)/04/EMR-II], Government of India for financial support. SJ and AH thank the CSIR, Government of India for research fellowships. HKF and SC would like to thank the Malaysian Government and Universiti Sains Malaysia for the Scientific Advancement Grant Allocation (SAGA) grant No. 304/PFIZIK/635003/A118.

Notes

¹ Receptor 1: Mp. 169–71°C; FT-IR (KBr): 3325, 3196, 3059, 2919, 1868, 1636, 1597,1557, 1541, 1352, 1249, 764, 712, 549 cm^− 1; ¹ H NMR (CDCl₃, 500 MHz): δ (ppm): 7.99–7.96(m, 2H), 7.59(t, 3H, J = 7.4 Hz), 6.94(s, 1H), 5.02(bs, 2H), 2.42(s, 3H). Complex 1: Mp. 106–08°C; FT-IR (KBr): 3365, 3325, 3059, 2919, 1918, 1636, 1597,1557, 1541, 1352, 1249, 764, 712, 549 cm^− 1; ¹H NMR (CDCl₃, 500 MHz): δ (ppm): 8.11(d, 2H, J = 7.8 Hz), 7.99–7.96(m, 2H), 7.59(t, 1H, J = 7.4), 7.48–7.45(m, 5H), 6.93(s, 1H), 5.73(bs, 2H), 2.45(s, 3H); Crystal data are as follows (CCDC No. 634315): C₁₈H₁₇N₃O₂, Mr = 307.35, 100.0(1) K, Triclinic, P-1, a = 8.88970(10) Å, b = 10.13780(10) Å, c = 10.39980(10) Å, α = 61.3550(10)°, β = 66.5820(10)°, γ = 71.2800(10)°, V = 744.822(13) ų, Z = 2, μ(Mo K_α) = 0.092 mm^− 1, Reflections collected/unique 34395/7789 [R(int) = 0.0364], R1(I>2σ(I)) = 0.0479, wR2 = 0.1269, R1(All data) = 0.0613, wR2 = 0.1373. Receptor 2: Mp. 150–52°C; FT-IR (KBr): 3405, 3312, 3184, 1638, 1597, 1466, 1389, 1241, 794, 552 cm^− 1; ¹H NMR (CDCl₃, 500 MHz): δ (ppm): 6.40(s, 1H), 4.86(bs, 2H), 2.29(s, 6H). Complex 2: Mp.118–20°C; FT-IR (KBr): 3335, 3180, 1662, 1599, 1317, 1298, 804, 714, 574 cm^− 1; ¹H NMR (CDCl₃, 500 MHz): δ (ppm): 8.11(d, 2H, J = 8 Hz), 7.57(t, 1H, J = 7.5 Hz), 7.46(t, 2H, J = 7.5 Hz), 6.39(s, 1H), 5.85(bs, 1H), 5.70(bs, 1H), 2.33(s, 6H); Crystal data are as follows (CCDC No. 634316): C₁₃H₁₅N₃O₂, Mr = 245.28, 100.0(1) K, Monoclinic, P2(1)/c, a = 6.7626(2) Å, b = 7.3958(2) Å, c = 25.0054(7) Å, α = 90°, β = 92.1460(10)°, γ = 90°, V = 1249.76(6) ų, Z = 4, μ(Mo K_α) = 0.090 mm^− 1, Reflections collected/unique 26058/3699 [R(int) = 0.0545], R1(I>2σ(I)) = 0.0525, wR2 = 0.1325, R1 = 0.0714 (All data), wR2 = 0.1506.