Next Article in Journal
The Reciprocal Principle of Selectand-Selector-Systems in Supramolecular Chromatography †
Next Article in Special Issue
Modeling of the Bioactivation of an Organic Nitrate by a Thiol to Form a Thionitrate Intermediate
Previous Article in Journal
Theoretical Study on the Second Hyperpolarizailities of Oligomeric Systems Composed of Carbon and Silicon π-Structures
Article Menu
Issue 11 (November) cover image

Export Article

Open AccessArticle

Diphenylcarbene Protected by Four ortho-Iodine Groups: An Unusually Persistent Triplet Carbene

Community-University Research Cooperation Center, Mie University, Tsu, Mie 514-8507, Japan
Department of Chemistry for Materials, Graduate School of Engineering, Mie University, Tsu, Mie 514-8507, Japan
Authors to whom correspondence should be addressed.
Academic Editor: Shunichi Fukuzumi
Molecules 2016, 21(11), 1545;
Received: 20 October 2016 / Revised: 8 November 2016 / Accepted: 11 November 2016 / Published: 15 November 2016
(This article belongs to the Special Issue Cutting-Edge Organic Chemistry in Japan)
PDF [2595 KB, uploaded 15 November 2016]


Diphenyldiazomethane with four iodine groups at the ortho positions and two tert-butyl groups at the para positions, i.e., bis(4-tert-butyl-2,6-diiodophenyl)diazomethane (1a-N2), was synthesized as a sterically hindered triplet carbene precursor. Irradiation of 1a-N2 in solution effectively generated the corresponding triplet diphenylcarbene 31a, which was characterized by UV-vis spectroscopy at low temperature, along with laser flash photolysis techniques at room temperature. The UV-vis spectrum of 31a was obtained by irradiating 1a-N2 in a 2-methyltetrahydrofuran matrix at 77 K. The ESR spectrum showed no triplet carbene signals, while a radical species was observed at the anticipated temperature of the decomposition of triplet carbene 31a. Transient absorption bands ascribable to 31a were observed by laser flash photolysis of 1a-N2 in a degassed benzene solution and decayed very slowly with a second-order rate constant (2k/εl) of 5.5 × 103·s1. Steady-state irradiation of 1a-N2 in degassed benzene afforded 9,10-diarylphenanthrene derivative 2a in a 31% yield. Triplet carbene 31a was also trapped by either oxygen (kO2 = 6.5 × 105 M1·s1) or 1,4-cyclohexadiene (kCHD = 1.5 M1·s1) to afford the corresponding ketone 1a-O or the diarylmethane 1a-H2. The carbene was shown to be much less reactive than the triplet diphenylcarbene that is protected by two ortho-iodo and two ortho-bromo groups, 31b. View Full-Text
Keywords: triplet carbene; diazo compound; photolysis; steric hindrance; substituent effect triplet carbene; diazo compound; photolysis; steric hindrance; substituent effect

Graphical abstract

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

Supplementary material


Share & Cite This Article

MDPI and ACS Style

Hirai, K.; Bessho, K.; Tsujita, K.; Kitagawa, T. Diphenylcarbene Protected by Four ortho-Iodine Groups: An Unusually Persistent Triplet Carbene. Molecules 2016, 21, 1545.

Show more citation formats Show less citations formats

Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Related Articles

Article Metrics

Article Access Statistics



[Return to top]
Molecules EISSN 1420-3049 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top