S?ntese e caracteriza??o de derivados do anidrido piromel?tico.

No presente estudo foram obtidos compostos isom?ricos, o 4,6- bis(aminocarbonil) ?cido isoft?lico (1) e 2,5-bis(aminocarbonil) ?cido tereft?lico (2) atrav?s da rea??o de am?nia anidra com anidrido piromel?tico em dimetil cetona a temperatura ambiente. O is?meros n?o foram isolados, e a mistura, nomeada PMNH2, foi caracterizada por m?todos f?sicos ? temperatura ambiente. C?lculos quantum-qu?micos foram realizados para estudo conformacional e compara??o com resultados experimentais. Um total de oito conforma??es do composto 1, seis do composto 2 e o 1,2,4,5 benzenotetracarboxilato (BTEC) foram simuladas por c?lculos ab initio, utilizando conjunto de fun??es base at? o n?vel B3LYP/6-311G__+. H? a forma??o de liga??es de hidrog?nio intramoleculares do tipo O?H_ _ _ O, N?H_ _ _O e O?H_ _ _ N, contudo essas se mostraram desestabilizar o conf?rmero. As estruturas que n?o formaram liga??es de hidrog?nio intramoleculares tem um conte?do energ?tico menor que as que formaram. Amostras cristalinas foram obtidas a partir da mistura em solu??o aquosa de PMNH2 com os ?ons Cu2+, Zn2+ e Co2+. Os cristais foram analisados por difra??o de raios X de monocristais. O processo de hidr?lise de amidas por cat?lise intramolecular explica a forma??o dos complexos 1,2,4,5 benzenotetracarboxilato de triaquacobre(II) di-hidratado (C10H20O18Cu2; C2=c; a = 12;116(2) ?, b = 18;091(4) ?, c = 9;5910(19)? e b = 112;90(3)o; z = 4); 1,2,4,5 benzenotetracarboxilato de diaquazinco(II) (C5H5O6Zn; P21=n; a = 5;246(1)?, b = 16;320(3)?, c = 8;114(2) ? e b = 97;95(1)o; z = 4) e 1,2,4,5 benzenotetracarboxilato diaquacobalto(II) tri-hidratado (C20H24O25Co3; P21=n; a = 9;521(2) ?, b = 11;075(2) ?, c = 14;020(3) ? e b = 104;13(2)o; z = 4). A presen?a de mol?culas de ?gua desempenham um importante papel na estrutura, como na coordena??o do metal de transi??o ou pela sua participa??o em diversas liga??es de hidrog?nio intermoleculares observadas. Foram observadas liga??es de hidrog?nio de moderadas a fracas, com o par?metros d(H _ _ _ O) e D(O_ _ _ O) da menor sendo 1;6911(38) e 2;5742(53)? e da maior liga??o de hidrog?nio 2;424 e 3;099?, respectivamente. Os metais de transi??o Cu2+ e Zn2+ s?o pentacoordenados por ?tomos de oxig?nios dos grupos carboxilatos e de mol?culas de ?gua. O Zn2+ apresentou como geometria de coordena??o uma bipir?mide triangular distorcida, o que ? in?dito para estruturas formadas com o BTEC. Os dois ?ons Co2+ presentes na estrutura cristalina s?o coordenados por seis ?tomos de oxig?nio e apresentam 3;5527(11)? de dist?ncia entre eles.In the present study isomers of 4,6-bis (aminocarbonyl) isophthalic acid (1), and 2,5-bis (aminocarbonyl) terephthalic acid (2) were obtained through reaction of anhydrous ammonia and pyromellitic anhydride in solution of dimethyl ketone at room temperature. The mixture (PMNH2) was characterized by physical methods. Quantum-chemical calculations were carried out for comparison with experimental results and for conformational analysis. Ab initio calculations up to the B3LYP/6-311G__+ level were used to simulate the gas-phase geometry of the conformers: eight conformations of 1, six of 2 and one of the 1,2,4,5 benzenetetracarboxylato (BTEC). Intramolecular O?H_ _ _ O, N?H_ _ _O and O?H_ _ _N hydrogen bonds were observed and correlated to molecular stability. Crystalline samples grow in water solution of PMNH2, Cu2+, Zn2+ and Co2+ ions and were analysed by means of X-ray single-crystals diffraction. Hydrolysis of the amide groups leads to formation of the salts: triaquacopper(II) 1,2,4,5 benzenetetracarboxylato dihydrate (C10H20O18Cu2; C2=c; a = 12:116(2)?, b = 18:091(4)?, c = 9:5910(19)? and b = 112:90(3)o; z = 4); diaquazinc(II) 1,2,4,5 benzenetetracarboxylato (C5H5O6Zn; P21=n; a = 5:246(1) ?, b = 16:320(3) ?, c = 8:114(2) ? and b = 97:95(1)o; z = 4) and diaquacobalt( II) 1,2,4,5 benzenotetracarboxylato trihydrate (C20H24O25Co3; P21=n; a = 9:521(2) ?, b = 11:075(2) ?, c = 14:020(3) ? and b = 104:13(2)o; z = 4). The water molecules have an important role in the crystal structures, specially in the hydrogen bonding interactions and metal coordination. The former can be classified in mean and weak hydrogen bonds, since the d(H _ _ _ O) and D(O_ _ _ O) geometrical parameters are in the range 1:691(4)?2:574(5)? for the shorter, and 2:424(3)?3:099(3)? for the longer hydrogen bonds, respectively. The ionic sites are penta-coordinated (for Cu2+ and Zn2+ transition metals) and hexa-coordinated (Co2+) by oxygen atoms from water and from carboxylate groups. In the crystal structure the Co2+ cations are separated by 3:553(1)?. The distorted trigonal bipyramid coordination geometry of the Zn2+ is unusual for BTEC compounds, and to date not reported in the scientific literature