Biphenylene

Biphenylene is a polycyclic hydrocarbon, composed of two benzene rings joined by two bridging bonds (as opposed to a normal ring fusion), thus forming a 6-4-6 arene system. The resulting planar structure{{cite journal

| title = The Crystal Structure of Biphenylene

| journal = J. Am. Chem. Soc.

| volume = 66

| doi = 10.1021/ja01240a012

| pages = 2035–2042

| year = 1944

| author = Waser, Jurg

| last2 = Lu

| first2 = Chia-Si

| authorlink2 = Lu Jiaxi (chemist)

| issue = 12}} was one of the first π-electronic hydrocarbon systems discovered to show evidence of antiaromaticity. The spectral and chemical properties show the influence of the central [4n] ring, leading to considerable interest in the system in terms of its degree of lessened aromaticity. Questions of bond alternation and ring currents have been investigated repeatedly. Both X-ray diffraction{{cite journal

| journal = Acta Crystallogr.

| volume = 20

| pages = 87–93

| year = 1966

| doi = 10.1107/s0365110x66000161

| author = Fawcett, J. K.

| title = A refinement of the structure of biphenylene

| author2 = Trotter, J.| issue = 1

| doi-access = free

| bibcode = 1966AcCry..20...87F

}} and electron diffraction{{cite journal

| journal = J. Am. Chem. Soc.

| volume = 96

| issue = 4

| pages = 1026–1032

| year = 1974

| author = Yokozeki, A.

| author2 = Wilcox Jr., C. F.

| author3 = Bauer, S. H.

| doi = 10.1021/ja00811a014

| title=Biphenylene. Internuclear distances and their root mean square amplitudes of vibration}} studies show a considerable alternation of bond lengths, with the bridging bonds between the benzenoid rings having the unusually great length of 1.524 Å. The separation of the rings is also reflected by the absence of the transmission of NMR substituent effects through the central [4n] ring. However, more sensitive NMR evidence, and particularly the shifting of proton resonances to high field, does indicate the existence of electron delocalization in the central [4n] ring.{{cite journal

| journal = Recl. Trav. Chim. Pays-Bas

| volume = 83

| issue = 12

| pages = 1230–1232

| year = 1964

| author1 = Katritzky, A. R. | title = Nuclear magnetic resonance evidence for partial bond fixation in biphenylene

| authorlink1 = Alan R. Katritzky

| author2 = Reavill, R. E.| doi = 10.1002/recl.19640831203

}}{{cite journal

| journal = Tetrahedron

| volume = 20

| issue = 5

| pages = 1179–1184

| doi = 10.1016/s0040-4020(01)98985-9

| year = 1964

| author = Fraenkel, G.

| title = NMR spectroscopy of benzocyclobutene and biphenylene

| author2 = Asahi, Y.

| author3 = Mitchell, M. J.

| author4 = Cava, M. P.}} This upfield shift has been interpreted in terms of diminished benzenoid ring currents, either with or without an accompanying paramagnetic ring current in the central [4n] ring. Magnetic susceptibility measurements also show a diminishing of both diamagnetic exaltation and diamagnetic anisotropy, relative to comparable pure [4n+2] systems, which is also consistent with a reduction of ring current diamagnetism.{{cite journal

| journal = J. Am. Chem. Soc.

| volume = 91

| issue = 8

| pages = 1991–1998

| year = 1969

| author = Dauben Jr., Hyp. J.

| author2 = Wilson, James D.

| author3 = Laity, John L.

| doi = 10.1021/ja01036a022

| title=Diamagnetic susceptibility exaltation in hydrocarbons}}{{cite journal

| journal = J. Am. Chem. Soc.

| volume = 93

| issue = 2

| pages = 556–557

| year = 1971

| author = Anet, F. A. L.

| author2 = Schenck, G.

| doi = 10.1021/ja00731a061

| title=Application of solvent effects to the study of diamagnetic and paramagnetic ring currents}}

The electronic structure of biphenylene in the gas phase has the HOMO at a binding energy of 7.8 eV.{{cite journal

| journal = J. Chem. Phys.

| volume = 142

| issue = 7

| pages = 074305

| year = 2015

| author = Lüder, Johann

| author2 = de Simone, Monica

| author3 = Totani, Roberta

| title = The electronic characterization of biphenylene—Experimental and theoretical insights from core and valence level spectroscopy

| doi = 10.1063/1.4907723 | pmid = 25702013

|display-authors=etal| hdl = 11368/2842819| bibcode = 2015JChPh.142g4305L

| url = https://arts.units.it/bitstream/11368/2842819/1/Lueder_2015.pdf

| hdl-access = free

}}

Biphenylene was first synthesized by Lothrop in 1941.{{cite journal

| journal = J. Am. Chem. Soc.

| volume = 63

| issue = 5

| pages = 1187–1191

| year = 1941

| author = Lothrop, W. C.

| doi = 10.1021/ja01850a007

| title=Biphenylene}}

The biphenylene structure can also be understood as a dimer of the reactive intermediate benzyne, which in fact serves as a major synthetic route, by heating the benzenediazonium-2-carboxylate zwitterion prepared from 2-aminobenzoic acid.{{OrgSynth|year = 1968|volume = 48|pages = 12|last1 = Logullo|first1 = Francis M.|last2 = Seitz|first2 = Arnold M.|last3 = Friedman|first3 = Lester|doi = 10.15227/orgsyn.048.0012|title = Benzenediazonium-2-Carboxylate and Biphenylene (Benzenediazonium, o-carboxy-, hydroxide, inner salt)|prep = CV5P0054|collvol = 5|collvolpages = 54}} Another approach is by N-amination of 1H-benzotriazole with hydroxylamine-O-sulfonic acid. The major product, 1-aminobenzotriazole, forms benzyne in an almost quantitative yield by oxidation with lead(IV) acetate, which rapidly dimerises to biphenylene in good yields.{{cite journal|first1 = C.D.|last1 = Campbell|first2 = C.W.|last2 = Rees|authorlink2 = Charles Rees|journal = J. Chem. Soc. C|title = Reactive intermediates. Part I. Synthesis and oxidation of 1- and 2-aminobenzotriazole|volume = 1969|issue = 5|pages = 742–747|year = 1969|doi = 10.1039/J39690000742}}

File:Dehydrobenzol aus Aminobenztriazol.svg

In the laboratory, flash vacuum pyrolysis of phthalic anhydride and other arylcarbonyls produces biphenylene.{{Kirk-Othmer|doi=10.1002/0471238961.flasmcna.a01.pub2|p=13|title=Flash Vacuum Pyrolysis|year=2018|first=Curt|last=Wentrup}}

Polycycles containing the biphenylene nucleus have also been prepared, some having considerable antiaromatic character.{{cite journal

| title = Cycloocta[def]biphenylene

| journal = J. Am. Chem. Soc.

| volume = 94

| issue = 7

| pages = 2532

| year = 1972

| author = Wilcox Jr., Charles F.

| author2 = Uetrecht, J. P.

| author3 = Grohman, K. K.

| doi=10.1021/ja00762a068}}{{cite journal

| title = Dicycloocta[1,2,3,4-def:1',2',3',4'-jkl]biphenylene. Benzenoid Atropism in a Highly Antiaromatic Polycycle

| journal = J. Am. Chem. Soc.

| volume = 105

| issue = 24

| pages = 7191–7192

| year = 1983

| author = Wilcox Jr., Charles F.

| author2 = Farley, Erik N.

| doi=10.1021/ja00362a040}}{{cite journal

| title = Dicyclooctabiphenylene. Synthesis and Properties

| journal = J. Am. Chem. Soc.

| volume = 106

| issue = 23

| pages = 7195–7200

| year = 1984

| author = Wilcox Jr., Charles F.

| author2 = Farley, Erik N.

| doi=10.1021/ja00335a055}}{{cite journal

| title = Cyclooctannelated Biphenylenes. Diagnosis of an Anomalous Bond Length by Analysis of Ring Current Geometric Factors

| journal = J. Org. Chem.

| volume = 50

| issue = 3

| pages = 351–356

| year = 1985

| author = Wilcox Jr., Charles F.

| author2 = Farley, Erik N.

| doi=10.1021/jo00203a013}}{{Cite thesis

| title = Dicyclooctabiphenylenes

| publisher = Cornell University

| date = 1984

| author = Farley, Erik Neil}} In general, additional 6-membered rings add further aromatic character, and additional 4-membered and 8-membered rings add antiaromatic character. However, the exact natures of the additions and fusions greatly affect the perturbations of the biphenylene system, with many fusions resulting in counter-intuitive stabilization by [4n] rings, or destabilization by 6-membered rings. This has led to significant interest in the systems by theoretical chemists and graph theoreticians.

A complete 2-dimensional carbon sheet with biphenylene-like subunits has been proposed {{cite journal

| journal = Revue Roumaine de Chimie

| volume = 13

| pages = 231

| year = 1968

| author =Balaban, A. T. }}

and was in-depth investigated by theoretical means, finding a technologically relevant direct band gap of ca. 1 eV, excitonic binding energies of ca. 500 meV and potential as a gas sensor. {{cite journal

| journal = J. Phys. Chem. C

| title = Nonzero gap two-dimensional carbon allotrope from porous graphene

| volume =116

| issue = 23

| pages = 12810–12813

| year = 2012

| author =G. Brunetto, P. A. S. Autreto, L. D. Machado, B. I. Santos, R. P. B. dos Santos, and D. S. Galvao| bibcode = 2012arXiv1205.6838B

| arxiv = 1205.6838

| doi = 10.1021/jp211300n

| s2cid = 103548116

}} {{cite journal

| journal = J. Chem. Phys.

| title = Many-body effects and excitonic features in 2D biphenylene carbon

| volume =144

| issue =2

| pages = 024702

| year = 2016

| author = Lüder J., Puglia C., Ottosson H., Eriksson O., Sanyal B., Brena B.| bibcode = 2016JChPh.144b4702L

| doi = 10.1063/1.4939273

| pmid = 26772582

}} {{cite journal

| journal =J. Mater. Chem. A

| title =Theoretical study of a tunable and strain-controlled nanoporous graphenylene membrane for multifunctional gas separation

| volume =4

| issue =39

| pages = 15015–15021

| year = 2016

| author = Zhu L., Jin Y.,Xue Q., Li X., Zheng H., Wu T. Ling C. | doi =10.1039/C6TA04456E

}}

Later, researchers synthesized a biphenylene sheet consisting of sp²-hybridized carbon atoms that formed four-, six-, and eight-membered rings on a smooth gold surface. A bottom-up two-step interpolymer dehydrofluorination of an adsorbed halogenated terphenyl molecule polymerization yielded ultraflat four- and eight-membered rings. The resulting allotrope was metallic.{{Cite journal|last1=Fan|first1=Qitang|last2=Yan|first2=Linghao|last3=Tripp|first3=Matthias W.|last4=Krejčí|first4=Ondřej|last5=Dimosthenous|first5=Stavrina|last6=Kachel|first6=Stefan R.|last7=Chen|first7=Mengyi|last8=Foster|first8=Adam S.|last9=Koert|first9=Ulrich|last10=Liljeroth|first10=Peter|last11=Gottfried|first11=J. Michael|date=2021-05-21|title=Biphenylene network: A nonbenzenoid carbon allotrope|url=https://www.science.org/doi/10.1126/science.abg4509|journal=Science|language=en|volume=372|issue=6544|pages=852–856|doi=10.1126/science.abg4509|issn=0036-8075|pmid=34016779|bibcode=2021Sci...372..852F |s2cid=234794559 }}

{{Reflist}}

Category:Antiaromatic compounds

Category:Hydrocarbons

Category:Biphenylenes