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

PDF - Published Version Download (2MB)

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 title Project leader Project code Project type Host-guest međudjelovanja u policikličkim sustavima [161124] Davor Margetić 098-0982933-3218 MZOS Organski i bioorganski procesi u osnovnom i elektronski pobuđenim stanjima [27544] Mirjana Maksić 098-0982933-2920 MZOS
Depositing User:	Davor Margetić
Date Deposited:	18 Oct 2013 07:54
URI:	http://fulir.irb.hr/id/eprint/808

Actions (login required)

View Item