Structure Elucidation of a Melam–Melem Adduct by a Combined Approach of Synchrotron X‐ray Diffraction and DFT Calculations

Kessler, Fabian K.; Burow, Asbjörn M.; Savaşçı, Gökçen; Rosenthal, Tobias; Schultz, Peter; Wirnhier, Eva; Ochsenfeld, Christian; Schnick, Wolfgang

doi:10.1002/chem.201901391

Cited by 7 publications

(6 citation statements)

References 49 publications

(167 reference statements)

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“…The morphology of melem, which was synthesized through direct calcination of melamine powder at 400 °C [Me(H), “H” stands for after heating], changes from the irregular shape to short rod-like structure after reorganization in water [Me(S), “S” stands for supramolecular assembly, Figures S1 and S2]. We prepared a series of supramolecular assemblies based on melem–melamine in water (referred here as x Me y M, where x / y is the molar ratio between melem and melamine, which is determined from the reported crystals; ,, x and/or y are omitted when equal to 1). 3MeM shows a uniform short-rod structure (Figure S3a 1 ,a 2 ) while irregular blocks were observed from MeM and Me2M adducts (Figures a,b and S3b), probably because of unmatching ratios between the melem and melamine species in the supramolecular assembly.…”

Section: Results and Discussionmentioning

confidence: 99%

Controllable Synthesis of Carbon Nitride Films with Type-II Heterojunction for Efficient Photoelectrochemical Cells

et al. 2020

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A simple, straightforward growth method of polymeric carbon nitride (CN) layers on a conductive substrate, with excellent photoelectrochemical activity owing to the formation of a type-II heterojunction by combining two distinct chemical growth methods is reported. The first layer consists of CN prepared from the calcination of a melem-melamine (MeM) adduct; the utilization of MeM enables the preparation of a processable paste which can be easily cast on the conductive substrate. To prepare the second layer, melamine vapor is introduced during calcination. After calcination, two well-connected CN layers with different electronic properties are formed, leading to the formation of a type-II heterojunction. The new CN films exhibit excellent photoelectrochemical properties with a photocurrent density up to 383 μA cm -2 at 1.23 V vs. RHE as well as an acceptable stability over 9 h in 10% (v/v) TEOA-containing 0.1 M KOH aqueous solution, thanks to the enhanced charge separation under illumination. Moreover, the CN films demonstrate good photoelectrochemical activity over a wide pH range, with photocurrent densities of 133, 80, and 118 μA cm -2 in 0.1 M KOH, 0.1 M Na2SO4, and 0.5 M H2SO4 aqueous solutions in the absence of any sacrificial agent, respectively.

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Section: Results and Discussionmentioning

confidence: 99%

Controllable Synthesis of Carbon Nitride Films with Type-II Heterojunction for Efficient Photoelectrochemical Cells

et al. 2020

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“…However, independent of the starting material, melem is always formed first, followed by a transformation back into triazine structures. A detailed discussion of these reaction pathways and this unexpected observation is provided in refs , , and (see Scheme ).…”

Section: Synthetic Approaches For Molecular S-heptazinesmentioning

confidence: 95%

“…Recently, Schnick et al have reinvestigated the thermolysis of melamine, the formation of melem, and also reverse transformation of melem into triazines in detail (see Scheme ). , The reaction steps are relatively complicated, and depending on the pressure–temperature–time (p–T–t) profile, especially the ammonia partial pressure is important, and different products may be obtained. Under ionothermal conditions–i.e., in salt melts such as LiCl/KCl or LiBr/KBr–a well characterized 2D network named poly(trazine imide) is formed.…”

Section: Synthetic Approaches For Molecular S-heptazinesmentioning

confidence: 99%

State of the Art in the Preparation and Properties of Molecular Monomeric s-Heptazines: Syntheses, Characteristics, and Functional Applications

et al. 2021

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This review gives an account on the fast expanding field of monomeric (or molecular) heptazines, at the exclusion of their various polymeric forms, often referred to as carbon nitrides. While examples of monomeric heptazines were extremely limited until the beginning of this century, the field has started expanding quickly since then, as has the number of reports on polymeric materials, though previous reviews did not separate these fields. We provide here a detailed report on the synthetic procedures for molecular heptazines. We also extensively report on the different achievements realized from these new molecules, in the fields of physical chemistry, spectroscopy, materials preparation, (photo)catalysis, and devices. After a comprehensive summary and discussion on heptazines syntheses and characteristics, we show that starting from well-defined molecules allows a versatility of approaches and a wide tunability of the expected properties. It comes out that the field of monomeric heptazines is now emerging and possibly heading toward maturity, while diverging from the one of polymeric carbon nitrides. It is likely that this area of research will quickly surge to the forefront of the search for active organic molecules, with special attention to the domains of catalysis and organic-based functional materials and devices.

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“…This vibration is the besti ndication to differentiate the two tautomeric forms by vibrational spectroscopy.T he experimental Raman spectrum shows this ring breathing vibration with av ery high intensity at 382 cm À1 . Scheme3.Synthesis of triphenyldithiocyamelurate (2), triethyldithiocyamelurate (3), trisodium thiocyamelurate (4)a nd tripotassium thiocyamelurate (5). Therefore, we assumet hat the thione form 1b is the preferred tautomeric form of 1 in the solids tate (see Scheme 4).…”

Section: Solution 13 Cn Mr Spectroscopymentioning

confidence: 99%

“…(few selected recent reviews:Y .W ang et al, [1] C. Hu et al, [2] J. Barrio et al, [3] F. K. Kessler et al [4] )I nm ost studies (photo)catalytic properties for highly attractive reactions such as water splitting and CO 2 reductiona re reported, which increasew itht he incorporation of hetero elements (sometimes called doping), including sulfur. It should be pointedout that the so-called sheet-like or layered and in many cases nano-structured "g-C 3 N 4 "m aterials are in fact hydrogen-containing s-triazine-and/or s-heptazine-based oligomers andp olymers, which are very easily obtained by thermolysis of melamineC 3 N 3 (NH 2 ) 3 or melamine precursors such as cyanamide or urea, yieldingt he molecular intermedi-ates melam (H 2 N) 2 C 3 N 3 -NH-C 3 N 3 (NH 2 ) 2 and melem C 6 N 7 (NH 2 ) 3 [5] and at higher temperatures the 1D polymer melon [C 6 N 7 (NH 2 )(NH)] n and 2D polymers like polyheptazine imide [C 6 N 7 (NH) 1.5 ] n ). [6] Hydrogen-free "g-C 3 N 4 "h ave been reported, but are usually not used in the numerous studies on catalytic applications.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Thiocyameluric Acid C₆N₇S₃H₃, Its Reaction to Alkali Metal Thiocyamelurates and Organic Tris(dithio)cyamelurates

Posern

Höhne

Böhme

et al. 2019

Chemistry A European J

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Thiocyameluric acidC 6 N 7 S 3 H 3 ,the tri-thio analogue of cyameluric acid, is ak ey compound for the synthesis of new s-heptazine (tri-s-triazine) derivatives. Here, two different routes for the synthesis of thiocyamelurica cid and its reaction to tris(aryldithio)-and tris(alkyldithio)cyamelurates C 6 N 7 (SSR) 3 are reported as well as transformation to alkali metal thiocyamelurates M 3 [C 6 N 7 S 3 ], M= Na, K. Thesec ompoundsw ere characterisedb yF TIR, Raman, solution 13 Ca nd 1 HNMR spectroscopies, thermal gravimetric analysis( TGA) and elementala nalysis. The three (de)protonation steps of thiocyamelurica cid were investigated by acid-base titration followed via UV/Vis absorptions pectroscopy.W hile it was not possible to determine the three pK a values, it could be postulated that the acid strength probably increases in the following order:cyanuric acid (C 3 N 3 O 3 H 3 ) < thiocyanuric acid (C 3 N 3 S 3 H 3 ) < cyameluric acid (C 6 N 7 O 3 H 3 ) < thiocyameluric acid (C 6 N 7 S 3 H 3 ). Single crystalso fN a 3 [C 6 N 7 S 3 ]·10 H 2 Oa nd K 3 [C 6 N 7 S 3 ]·6 H 2 Ow ere obtained and the structures analyzed by single crystal X-ray diffraction. Additionally,q uantum chemicalc alculationsw ere performed to get insights into the electronic structure of thiocyameluric acid and to clarify the thiol-thione tautomerism.B ased on ac omparison of calculated and measuredv ibrational spectra it can be concluded that thiocyamelurica cid and the di-and mono-protonated anionsexist in the thione form.Scheme1.Principalstructures of the s-triazine derived cyanurates [C 3 N 3 O 3 ] 3À ,a nd the s-heptazine derived cyamelurates [C 6 N 7 O 3 ] 3À and their thio analogues. For ab etterc omparisonw ith cyameluricacid andcyamelurates we named 2,5,8-trimeracpto-tri-s-triazine and its derivatives thiocyameluric acid, thiocyameluratesa nd the disulfidesa re named dithiocyamelurates.[a] C.Supporting Information and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.org/10.

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Structure Elucidation of a Melam–Melem Adduct by a Combined Approach of Synchrotron X‐ray Diffraction and DFT Calculations

Cited by 7 publications

References 49 publications

Controllable Synthesis of Carbon Nitride Films with Type-II Heterojunction for Efficient Photoelectrochemical Cells

Controllable Synthesis of Carbon Nitride Films with Type-II Heterojunction for Efficient Photoelectrochemical Cells

State of the Art in the Preparation and Properties of Molecular Monomeric s-Heptazines: Syntheses, Characteristics, and Functional Applications

Synthesis of Thiocyameluric Acid C₆N₇S₃H₃, Its Reaction to Alkali Metal Thiocyamelurates and Organic Tris(dithio)cyamelurates

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Structure Elucidation of a Melam–Melem Adduct by a Combined Approach of Synchrotron X‐ray Diffraction and DFT Calculations

Cited by 7 publications

References 49 publications

Controllable Synthesis of Carbon Nitride Films with Type-II Heterojunction for Efficient Photoelectrochemical Cells

Controllable Synthesis of Carbon Nitride Films with Type-II Heterojunction for Efficient Photoelectrochemical Cells

State of the Art in the Preparation and Properties of Molecular Monomeric s-Heptazines: Syntheses, Characteristics, and Functional Applications

Synthesis of Thiocyameluric Acid C6N7S3H3, Its Reaction to Alkali Metal Thiocyamelurates and Organic Tris(dithio)cyamelurates

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Synthesis of Thiocyameluric Acid C₆N₇S₃H₃, Its Reaction to Alkali Metal Thiocyamelurates and Organic Tris(dithio)cyamelurates