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Proton Affinities of Didehydroporphyrin and Subporphyrin in Ground and Excited States Obtained by Quantum Chemical Calculations

Glasovac, Zoran; Vazdar, Mario; Margetić, Davor (2009) Proton Affinities of Didehydroporphyrin and Subporphyrin in Ground and Excited States Obtained by Quantum Chemical Calculations. Croatica Chemica Acta, 82 (1). pp. 63-70. ISSN 0011-1643

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Abstract

Quantum-chemical calculations were used to investigate molecular and electronic properties of porphyrin and subporphyrin. Their basicities were estimated in ground and excited states. It was found that multiple proton - nitrogen lone-pair coordination plays an important role in acid/base properties of the studied molecules. Lone pair-lone pair interactions in didehydroporphyrin and energetic stabilization of its protonated form lead to the increase of a proton affinity compared to porphyrin by 18 kcal mol(-1). A planarization of the protonated (dehydroporphyrin) structure leads to the complete reversal of the pi-electron ring currents indicating aromaticity of the protonated form. On the other hand, calculations indicate that subporphyrin is slightly (by 5 kcal mol(-1)) more basic than porphyrin, which was explained by non-planar geometry, imposed by smaller ring size.

Item Type: Article
Uncontrolled Keywords: DFT calculations; NICS; TDDFT; proton affinity; basicity; density-functional theory; molecular-orbital calculations; neutral organic-bases; gas-phase; ab-initio; electronic-structure; conjugated systems; hydrogen-bonds; subphthalocyanines; aromaticity
Subjects: NATURAL SCIENCES > Chemistry
Divisions: Division of Organic Chemistry and Biochemistry
Projects:
Project titleProject leaderProject codeProject type
Host-guest međudjelovanja u policikličkim sustavima[161124] Davor Margetić098-0982933-3218MZOS
Organski i bioorganski procesi u osnovnom i elektronski pobuđenim stanjima[27544] Mirjana Maksić098-0982933-2920MZOS
Depositing User: Davor Margetić
Date Deposited: 18 Oct 2013 07:54
Last Modified: 10 Feb 2014 09:53
URI: http://fulir.irb.hr/id/eprint/808

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