Synthesis of 25,27-[N,N'-DI-((ethoxy)benzyl)propylenediamine]-26,28-dimethoxy-p-tert-butylcalix[4]arene dihydrochloride and investigation of its basicity and complexation with some transition metal ions

Abstract

2 5, 2 7- [~iN, N(+,ข)~i-di-((ethoxy)benzyl)propylenediamine] -26,28-dimethoxy-~ip-ter~i-tbutylcalix[4]arene dihydrochloride ~b(7, L.21iCI),~b an ammoniumderivative of diaza calix[4] arene, was prepared by methylating phenoxy oxygen ofdialdehyde calix[4]arene with ~bCH(,3)I.~b The methylated dialdehyde was then reactedwith 1,3-diaminopropane to give a Schiff base compound which was then reduced with~bNaBH(,4)~b and protonated with 2% ~bHCI~b in ~bCH(,3)OH.~b The confirmational isomerism of~bL.2HCl~b was studied by ~b('1)H NMR~b spectroscopy. ~b('1)H NMR~b spectra of ~bL.21lCI~b in~bCDCI(,3)~b and in ~bDMSO-d(,6)~b showed that the calix[4]arene moiety orientated in mixedconformations. However, the ~b('1)H NMR~b spectrum in ~bCD(,3)OD~b indicated coneconformation. Gradual additions of ~bCD(,3)OD~b into a ~bCDCI(,3)~b solution of ~bL.2XCI~brevealed that intermolecular hydrogen bonding between methanol and~bCH(,3)OAr-t-C(,4)H(,9)~b held the calix[4] arene framework in cone conformation.Variable temperature experiments of ~bL.21iCI~b in a mixed solvent of ~bCD(,3)OD/CDl(,3),~bimplied a possible mechanism of phenyl ring movement and suggested that a pinchedcone conformation was preferred at -40 (+,ฐ) In addition, protonation constants of ~bL~b were calculated in methanolic solutionof ~b1x10('-2) M Bu(,4)NCF(,3)SO(,3)~b by potentiometric titration. ~bLog~b ~iK(,1)~i (Log ~iK(,2))~ivalues of the first protonation (second protonation) were 10.06 (6.67), 9.97 (6.75),9.61 (6.64), 9;75 (6.77) and 9.69 (6.68) at 20, 23, 25, 27 and 30 (+,ฐ) respectively.Calculated thermodynamic functions, ~b(+,D)H(,1), (+,D)H(,2), (+,D)S(,1)~b and (+,D)S(,2) The first and second protonationswere -67 kJ/mol, 3 kJ/mol, -38 kJ/mol K and 137 kJ/mol K, respectively. Complexationstudies of ~bL~b with Zn('2+) and Cu('2+) ions by the same method showed that ~b L~b could not formcomplexes with both ions.