Investigation theoretical of nucleophilic attack to four- coordinate verdohime Ni (II) withby NH2‾ using a B3LYP method

Document Type : Research Article


1 Department of Chemistry, Faculty of Science,Lorestan University, khorram abad,iran

2 Department of Chemistry/ Faculty of Science/Lorestan University/khorram abad/iran


The ring opening due to nucleophilic addition reactions of〖 NH〗_2^- to 〖[Ni^II (OP)]〗^+ have been investigated using B3LYP method. 6-31G basis set has been employed for optimization of the structures. Presence of Nickel atom leads to the increase of positive charge on carbon atoms adjacent to the oxygen atom in〖 [Ni^II (OP)]〗^+ relative to 5- oxaporphyrin. An intermediate is initially formed by nucleophilic attack to one of the aforesaid carbon atoms which is then directly converted to the helical open-ring complex, [Ni^II (BNü)] by passing through a transition state. In the latter products the helical ligand composes a structure in which the Nickel ion is trapped between planar and tetrahedron coordination, which has been confirmed with experimental work. Even though the most positive center for the nucleophile to attack is Nickel atom in 〖 [Ni^II (OP)]〗^+, it has been shown that such addition does not lead to a stable intermediate. A NBO analysis has been performed aiming to investigate the relative stabilities of all species involved in the process. A key point is the fact that interaction of nucleophile with Nickel atom of 〖 [Ni^II (OP)]〗^+, decreases interaction of the porphyrin ring with Nickel, which can be translated as an effective perturbation in the complex planar structure and thus formation of an unstable species [NüNi^II(OP)]. Another point from such analysis has determined that connection of nucleophile to oxo-carbon in 〖 [Ni^II (OP)]〗^+, diminishes strength of C-O bond in the intermediate. Weakening of this bond becomes profound in transition state species, which then leads to the open chain helical product. These key points and all other NBO findings have been corroborated by the results obtained from molecular orbital calculations.


Main Subjects