The anionic cyclodextrins (CDs), heptakis[6-(3-thiopropionate)-6-deoxy]-β-CD, heptakis[(6-(thio-ethanoate)-6-deoxy]-β-CD and partially phosphorylated 6-(aminoethylphosphate)-6-deoxy-β-CD as triethylammonium salts, bpsp.NHEt 3 , bpse.NHEt 3 and bphos.NHEt 3 , respectively, interacted with the positively charged picrate salt of heptakis[6-(guanidino)-6-deoxy]-β-CD, bguan.picrate, to form heterodimers as shown by NMR spectroscopic and microcalorimetric isothermal titration calorimetry (ITC) titrations in solution. Association constants, K a (M− 1) in DMSO-d 6 and in DMSO-d 6–H2O (80/20, v/v) were: bguan.picrate/bpsp.NHEt 3 , 6.4 × 105 and 5.9 × 104; bguan.picrate/bpse.NHEt 3 , 4.2 × 104 and 1.2 × 104; ITC data in DMSO agreed with those above: bguan.picrate/bpsp.NHEt 3 , K a = 4.7 ± 0.1 × 105 M− 1, ΔH = − 83.97 kJ mol− 1, ΔS = − 173.19 J mol− 1 K− 1; bguan.picrate/bpse.NHEt 3 , K a = 2.4 ± 0.2 × 105 M− 1, ΔH = − 88.49 kJ mol− 1 and ΔS = − 182.27 J mol− 1 K− 1. Heterodimers are highly stable in DMSO and less stable in DMSO–H2O. Multivalency in the interactions is manifested by positive cooperativity, negative enthalpy of formation (ΔH) and sizeable negative entropy (ΔS), in support of the development of well-ordered supramolecular structures in solution.