Oxidative homolysis of organochromium macrocycles

Journal Article · Wed Mar 06 04:00:00 EST 1991 · Inorganic Chemistry; (United States)

DOI:https://doi.org/10.1021/ic00005a046· OSTI ID:5900460

Steffan, C R; Espenson, J H; Bakac, A ^[1]

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1. Iowa State Univ., Ames (United States)

The complexes RCrL(H{sub 2}O){sup 2+} (R = alkyl, aralkyl; L = 1,4,8,12-tetraazacyclopentadecane) are oxidized by Ru(bpy){sub 3}{sup 3+} and {sup 2}E Cr(bpy){sub 3}{sup 3+}. The one-electron oxidized species RCrL(H{sub 2}O){sup 3+} undergoes subsequent homolysis; the R{sup {center dot}} radicals so produced may react with certain metal complexes, or they dimerize, depending on conditions. The rate constants for the rate-controlling step, electron transfer from RCrL(H{sub 2}O){sup 2+} to Ru(bpy){sub 3}{sup 3+} or *Cr(bpy){sub 3}{sup 3+}, were measured by laser flash photolysis for an extensive range of R groups. For Ru(bpy){sub 3}{sup 3+}, the rate constants range from 14.2 L mol{sup {minus}1} s{sup {minus}1} (R = CH{sub 3}) to 1.05 {times} 10{sup 9} (R = 4-CH{sub 3}C{sub 6}H{sub 4}CH{sub 2}); for *Cr(bpy){sub 3}{sup 3+}, the corresponding values are 2.8 {times} 10{sup 6} and 1.55 {times} 10{sup 9} L mol{sup {minus}1} s{sup {minus}1}. In both series, the order of rate constants is methyl < primary alkyl < secondary alkyl < secondary alkyl < aralkyl. The plots of log k versus the gas-phase ionization potentials of R{sup {center dot}} are linear, in accord with the rate-controlling step being electron transfer.

• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 5900460
• Journal Information: Inorganic Chemistry; (United States), Journal Name: Inorganic Chemistry; (United States) Vol. 30:5; ISSN 0020-1669; ISSN INOCA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical &amp; Physicochemical Properties
ALKENES
AZINES
BIPYRIDINES
CHEMICAL REACTIONS
CHROMIUM COMPLEXES
COMPLEXES
CYCLOALKENES
CYCLOPENTADIENE
DATA
DIENES
EXPERIMENTAL DATA
HETEROCYCLIC COMPOUNDS
HYDROCARBONS
INFORMATION
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANOMETALLIC COMPOUNDS
POLYENES
PYRIDINES
REDOX REACTIONS
RUTHENIUM COMPLEXES
TRANSITION ELEMENT COMPLEXES