Stepwise charge transfer complexation of some pyrimidines with σ-acceptor iodine involving a new unconventional acceptor

Interactions of some pyrimidine derivatives, 4-amino-2,6-dimethylpyrimidine, kyanmethin, (4AP), 2-amino-4,6-dimethylpyrimidine (2AP), 2-aminopyrimidine (AP), 2-amino-4-methylpyrimidine (AMP), 2-amino-4-methoxy-6-methylpyrimidine (AMMP), and 4-amino-5-chloro-2,6-dimethylpyrimidine (ACDP) as electron donors, with iodine (I2), as a typical σ-electron acceptor, have been studied. Electronic absorption spectra of these interactions in several organic solvents of different polarities have performed instant appearance of clear charge transfer (CT) bands. Formation constants (KCT), molar absorption coefficients (ɛCT) and thermodynamic properties, ΔH, ΔS, and ΔG, of these interactions have been determined and discussed. Electronic absorption spectra of the solutions of the synthesized pyrimidines–iodine, P–I2, CT complexes have shown the characteristic bands of the triiodide ion, I3−. UV/vis spectral tracking of these interactions have shown that by lapse of time the first formed CT complex, P–I2, is transformed to the corresponding triiodide complex, P+I.I3−, then, the later interacts as a new unconventional acceptor and it forms a CT complex of the form (P).(P+I.I3−). Elemental analyses of these solid complexes have indicated the stoichiometric ratio 2:2, or formally 1:1, P:I2.

Interactions of some aminopyrimidines, as electron donors, with the σ-acceptor, iodine, have led to the formation of CT complexes having the stoichiometric ratio 2:2 (donor (P):acceptor(I2)), or formally 1:1. Thus, the well known triiodide complex, P+I.I3−, resulting in situ, is a new acceptor that interacts with another molecule of the donor (P) to form a CT complex having the form, (P).(P+I.I3−). Spectral tracking of these interactions have shown the stepwise formation of the triiodide CT complex.Figure optionsDownload as PowerPoint slide