triphenylene

Triphenylene was first separated by German Chemists Von E. Schmidt and G. Schultz in 1880 from the pyrotic product of the thermal decomposition of benzene vapor.{{Cite web |last=Buess |first=Charles M. |last2=Lawson |first2=D. David |date=2002-05-01 |title=The Preparation, Reactions, and Properties of Triphenylenes. |url=https://pubs.acs.org/doi/pdf/10.1021/cr60206a001?casa_token=7KeP1v7_G58AAAAA%3Aunm--ifUIDWNiR3XZ8cF-OQauuMA082Ej8w7llq_i4oTaH7vpqNqBaPuTLfQNf2ZvH5dYHFxqO17iWOE& |access-date=2025-02-19 |website=ACS Publications |language=EN |doi=10.1021/cr60206a001?casa_token=7kep1v7_g58aaaaa:unm--ifuidwnir3xz8cf-oqauuma082ej8w7llq_i4otah7vpqnqbaputlfqnf2zvh5dyhfxqo17iwoe}} Though triphenylene is previously referred to as chrysene, Schmidt and Schultz realized that it is an isomer of chrysene, and successfully identified and named it as triphenylene.{{Cite journal |last=Schmidt |first=H. |last2=Schultz |first2=G. |date=1880 |title=II. Ueber Diphenylbenzole |url=https://chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/jlac.18802030107 |journal=Justus Liebigs Annalen der Chemie |language=en |volume=203 |issue=1-2 |pages=118–137 |doi=10.1002/jlac.18802030107 |issn=1099-0690}}

Later in 1907, Carl Mannich first synthesized triphenylene through a two-step reaction from cyclohexanone and confirmed its planar structure. Through predicted condensation of cyclohexanone following the pathway below, he obtained dodecahydrotriphenylene(C₁₈H₃₀).{{Cite journal |last=Mannich |first=C. |date=1907 |title=Über die Kondensation des Cyclohexanons |url=https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/cber.19070400122 |journal=Berichte der deutschen chemischen Gesellschaft |language=en |volume=40 |issue=1 |pages=153–165 |doi=10.1002/cber.19070400122 |issn=1099-0682}}

File:Potential_condensation_pathways.png

Mannich then dehydrogenated dodecahydrotriphenylene into triphenylene with two methods: zinc dust distillation and copper-catalyzed dehydrogenation. He confirmed the product was identical to the pyrolysis product from benzene by reproducing Schmidt and Schultz's experiment and comparing the samples. Mannich also characterized triphenylene's properties, derivatives, and oxidation reactions, and confirmed it as a fully aromatic polycyclic hydrocarbon.

File:First_synthesis_of_Triphenylene.png

Triphenylene can be isolated from coal tar. It can also be synthesized in various ways.

One method is trimerization of benzyne.{{OrgSynth |first1=H. |last1=Heaney |first2=I. T. |last2=Millar |year=1960 |title=Triphenylene |volume=40 |pages=105 |doi=10.15227/orgsyn.040.0105}} This pathway first diazotizes and iodinates o-bromoaniline through HCl, NaNO₂, and KI to produce o-bromoiodobenzene with a yield of 72 - 83%. Then form o-bromophenyl lithium using Li and ether. Add benzene to the organolithium intermediate to get triphenylene with a yield of 53 - 59%. Impurities of biphenyl are then removed with steam distillation.{{OrgSynth|first1=H.|last1=Heaney|first2=I. T.|last2=Millar|year=1960|title=Triphenylene|volume=40|pages=105|doi=10.15227/orgsyn.040.0105}}

File:Triphenylene_synthesis_scheme_2.jpg

Another method involves trapping benzyne with a biphenyl derivative.{{cite journal |doi=10.15227/orgsyn.099.0174|author=Katie A. Spence, Milauni M. Mehta, Neil K. Garg| title=Synthesis of Triphenylene via the Palladium–Catalyzed Annulation of Benzyne |year=2022 |journal=Organic Syntheses |volume=99 |pages=174–189|s2cid=250383238 |doi-access=free }} This method started with removing the trimethylsilyl group from 2-(trimethylsilyl)phenyl trifluoromethanesulfonate using cesium fluoride, generating benzyne. Benzyne then reacts with 2-bromobiphenyl in the presence of Pd(dba)₂ and tri(o-tolyl)phosphine as catalysts and produces triphenylene with a yield of 76%.{{cite journal |author=Katie A. Spence, Milauni M. Mehta, Neil K. Garg |year=2022 |title=Synthesis of Triphenylene via the Palladium–Catalyzed Annulation of Benzyne |journal=Organic Syntheses |volume=99 |pages=174–189 |doi=10.15227/orgsyn.099.0174 |s2cid=250383238 |doi-access=free}}

File:Triphenylene_synthesis_scheme_1.jpg

Triphenylene and its derivatives have been widely used in discotic liquid crystal and organic electronics as the core moiety due to its robust discotic molecular architecture. {{Cite journal |last=Tao |first=Lei |last2=Xie |first2=Yang |last3=Zhao |first3=Ke-Xiao |last4=Hu |first4=Ping |last5=Wang |first5=Bi-Qin |last6=Zhao |first6=Ke-Qing |last7=Bai |first7=Xiao-Yan |date=2024-07-01 |title=Triphenylene trimeric discotic liquid crystals: synthesis, columnar mesophase and photophysical properties |url=https://pubs.rsc.org/en/content/articlelanding/2024/nj/d4nj01693a |journal=New Journal of Chemistry |language=en |volume=48 |issue=26 |pages=12006–12014 |doi=10.1039/D4NJ01693A |issn=1369-9261}}{{Cite journal |last=Saleh |first=Moussa |last2=Park |first2=Young-Seo |last3=Baumgarten |first3=Martin |last4=Kim |first4=Jang-Joo |last5=Müllen |first5=Klaus |date=2009 |title=Conjugated Triphenylene Polymers for Blue OLED Devices |url=https://onlinelibrary.wiley.com/doi/abs/10.1002/marc.200900332 |journal=Macromolecular Rapid Communications |language=en |volume=30 |issue=14 |pages=1279–1283 |doi=10.1002/marc.200900332 |issn=1521-3927}}{{Cite journal |last=Hoang |first=Mai Ha |last2=Cho |first2=Min Ju |last3=Kim |first3=Kyung Hwan |last4=Cho |first4=Mi Yeon |last5=Joo |first5=Jin-soo |last6=Choi |first6=Dong Hoon |date=2009-11-30 |title=New semiconducting multi-branched conjugated molecules based on π-extended triphenylene and its application to organic field-effect transistor |url=https://www.sciencedirect.com/science/article/abs/pii/S0040609009011481?casa_token=s_Ln3hky17QAAAAA:ene6-g24tnI9i3TLoxzOlbgtt5Su5aLpYAu-0S90OXvziHofAYisJJ7txoAOEEUh_KkNRwtgtUo |journal=Thin Solid Films |series=8th International Conference on Nano-Molecular Electronics |volume=518 |issue=2 |pages=501–506 |doi=10.1016/j.tsf.2009.07.030 |issn=0040-6090}}

File:Stacking_of_Triphenylene_molecule.png

Due to its planar structure and π-conjugated system, triphenylene has a rigid discotic structure. This enables it to self-assemble and form highly ordered, long, cylindrical columns. The columnar mesophases provide a direct pathway for charge carriers(electrons or holes) and avoid interruption from scattering and trapped effects in disordered materials. This leads to efficient charge transport along the stacking direction.{{Cite journal |last=Wöhrle |first=Tobias |last2=Wurzbach |first2=Iris |last3=Kirres |first3=Jochen |last4=Kostidou |first4=Antonia |last5=Kapernaum |first5=Nadia |last6=Litterscheidt |first6=Juri |last7=Haenle |first7=Johannes Christian |last8=Staffeld |first8=Peter |last9=Baro |first9=Angelika |last10=Giesselmann |first10=Frank |last11=Laschat |first11=Sabine |date=2016-02-10 |title=Discotic Liquid Crystals |url=https://pubs.acs.org/doi/10.1021/acs.chemrev.5b00190 |journal=Chemical Reviews |volume=116 |issue=3 |pages=1139–1241 |doi=10.1021/acs.chemrev.5b00190 |issn=0009-2665}} Tripenylene derivatives, with flexible aliphatic side chains, can modulate intermolecular interactions. This maintains molecular mobility under a wide temperature range and avoids excessive crystallization, and corresponding bad processability and solubility. Triphenylene derivatives also can be synthesized through well-established routes like the Suzuki–Miyaura cross-coupling reaction. Its functional groups can be introduced easily and used to adjust its properties.{{Cite web |date=2016-12-17 |title=Suzuki-Miyaura Coupling |url=https://chem.libretexts.org/Bookshelves/Inorganic_Chemistry/Supplemental_Modules_and_Websites_(Inorganic_Chemistry)/Catalysis/Catalyst_Examples/Suzuki-Miyaura_Coupling |access-date=2025-02-19 |website=Chemistry LibreTexts |language=en}}

Recent studies synthesized new polymer structures incorporating triphenylene units and found that these materials exhibit high photoluminescence and electroluminescence efficiencies. Their emission spectra are well-suited for blue light applications, demonstrating stability and promising performance for next-generation blue emitters.

Due to its delocalized system, rigid structure, stability, and adjustable structures, triphenylene can be used in the synthesis of Metal-Organic Frameworks (MOFs) and Covalent Organic Frameworks (COFs).{{Cite journal |last=Contreras-Pereda |first=Noemí |last2=Pané |first2=Salvador |last3=Puigmartí-Luis |first3=Josep |last4=Ruiz-Molina |first4=Daniel |date=2022-06-01 |title=Conductive properties of triphenylene MOFs and COFs |url=https://www.sciencedirect.com/science/article/pii/S0010854522000546 |journal=Coordination Chemistry Reviews |volume=460 |pages=214459 |doi=10.1016/j.ccr.2022.214459 |issn=0010-8545|hdl=10261/271043 |hdl-access=free }}{{Cite thesis |last=Contreras Pereda |first=Noemí |title=Synthesis and electronic characterization of triphenylene-based materials |date=2021 |url=https://ddd.uab.cat/record/257769?ln=en}} Similar to the properties mentioned in DLC applications, triphenylene and its derivatives have high conductivity, and further affect the conductivity of MOFs and COFs. HATP-based 2D MOFs Ni₃(HITP)₂ single crystals can reach conductivities as high as 150 S/cm at 0K.

File:Chemical_structure_of_a_TP_molecule.png

File:Synthesis_of_triphenylene_derivatives_hexaalkoxytriphenylenes(HAT).jpg

The rigid planar structure and three-fold symmetry of triphenylene also make it suitable for honeycomb-like 2D layered materials. This enables supramolecular interlayer aggregation of TP-based MOFs and COFs and increases the stability and conductivity of the structure. It will also create uniform nanopores, which lead to high porosity and facilitate gas storage, molecular sieving, and ion exchange.

Multiple substitution sites of triphenylene bring multifunctionality to TP-base MOFs and COFs. Depending on the different functional groups, the physical and chemical properties of frameworks can be modified easily. In addition, due to the high chemical stability of triphenylene, it is adaptable to various synthesis methods like solvothermal synthesis, layer-by-layer assembly, microfluidic synthesis, interfacial synthesis, etc.

File:Formation_scheme_of_TP-based_2D_MOFs_and_TP-based_2D_COFs.png

File:Synthesis_of_Ni3(HITP)2_thin_films_through_ammonia_diffusion.png

{{reflist}}

• [http://ois.nist.gov/pah/sp922_Detail.cfm?ID=100 Polycyclic Aromatic Hydrocarbon Structure Index] {{Webarchive|url=https://web.archive.org/web/20080215085302/http://ois.nist.gov/pah/sp922_Detail.cfm?ID=100 |date=2008-02-15 }}

{{PAHs}}

Category:Polycyclic aromatic hydrocarbons

Category:Tetracyclic compounds