Thermal studies on purine complexes. V. Thermal behaviour of tetrachloropalladates of theophylline and theobromine and theophylline complexes of Cd(II) and Hg(II)

Colacio-Rodríguez, E.; Salas-Peregrín, J.M.

doi:10.1016/0040-6031(84)80005-2

Cited by 14 publications

(7 citation statements)

References 16 publications

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“…The acidic character is actually remarkable when the substituent on N(7) is a proton (theophylline, 1). This prediction of our model totally agrees with the experimental observations that have previously been reported [3,9], where theophylline can be easily deprotonated in presence of a basic late transition metal precursor or a late transition metal precursor in basic conditions, yielding N(7) coordinated species. The preferential coordination site at N(7), which has also been theoretically studied [3,61], has previously been proposed not only for theophylline derivatives but also for analogous molecules such as guanine and adenine.…”

Section: Resultssupporting

confidence: 92%

“…Thus, an interaction with a rich metal center is also predicted. In fact, N(9) complexes of caffeine are well known [2,60,[62][63][64][65][66], and there are examples reported with theobromine [3,[67][68][69]. The latter one also displays an acidic nature (LUMO) onto N(1), substituted by a proton.…”

Section: Resultsmentioning

confidence: 94%

“…Then, the main objective was to study the coordination chemistry of the new ligands obtained toward palladium, in an attempt to synthesize NHC-Pd compounds, and contrast their behavior with the previously known examples of methylated xanthines-palladium species [2][3][4][5][6][7][8].…”

Section: Resultsmentioning

confidence: 99%

“…Also, the coordination chemistry of the xanthine derivatives toward palladium(II) was investigated and contrasted with their unmodified counterparts [2][3][4][5][6][7][8], determining if the N(1,7) or C (8) hapticity is favored. In addition, a theoretical study of the acidity-basicity and orbital energies of each xanthine, 1-3, was performed, observing a match between theoretical results and the experimental evidence in the modification of these methylated xanthines and their coordination chemistry toward palladium.…”

Section: Introductionmentioning

confidence: 99%

“…In this sense, several efforts have been made to study their coordination chemistry toward ''essential metals'' [3] and their interaction with transition metals [3][4][5][6][7][8]. For instance, Williams [2] et al reported an analog to cis-platin with caffeine, Pt(caff) 2 Cl 2 , and there are reports in which the thermal behavior of these xanthines under physiological conditions has been studied [3][4][5][6]. Also, Taube and coworkers [7] proposed a C(8) coordination to ruthenium in the unmodified caffeine and theobromine ligands, and a mixed N-C, coordination fashion in theophylline.…”

Section: Introductionmentioning

confidence: 99%

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Studies on the coordination chemistry of methylated xanthines and their imidazolium salts. Part 1: benzyl derivatives

Landaeta

Rodríguez-Lugo

Rodríguez-Arias

et al. 2009

Transition Met Chem

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New imidazolium salts derived from the natural methylated xanthines theophylline, theobromine and caffeine, namely 1,3-dimethyl-9-benzylxanthinium bromide (tphBzBr, 1a), 3,7-dimethyl-9-benzylxanthinium bromide (tbrBzBr, 2a) and 1,3,7-trimethyl-9-benzylxanthinium bromide (caffBzBr, 3a), are reported. Also, the disubstituted analog of 1a, 1,3-dimethyl-7,9-dibenzylxanthinium bromide (tphBz 2 Br, 1a 0 ) was identified and characterized by NMR. The coordination chemistry of ligands 1a-3a toward palladium, and some theoretical aspects of the unmodified theophylline, theobromine and caffeine are studied. Our results prove that the theophylline derivative has the thermodynamic tendency to form N-bonded species, even when an equilibrium between the Pd-NHC and the ''theophyllinate'' was observed spectroscopically, due to the anisotropy of the NHC ligand. To confirm the Ncoordination, the solid state structure of the new ''theophyllinate'' species PdBr 2 (tphBz-H) 2 (4), derived from 1a, was determined by X-ray diffraction. The analog with theobromine, ligand 2a, coordinates to palladium via N1, in an analogous manner to 1a, and a mixture of the cis/trans isomers of its palladium complex is obtained. On the other hand, since there is no possibility of N-coordination in 3a, this caffeine derivative forms a Pd-NHC compound after deprotonation with a strong base. Both the theoretical results and the experimental evidence are in accordance, in terms of the predicted coordination sites or possibility of modification of the selected methylated xanthines to obtain new ligands.

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