A Facile Route to Metal Nitride Clusterfullerenes by Using Guanidinium Salts: A Selective Organic Solid as the Nitrogen Source

Abstract

Using guanidinium salts 1 and 2 as the new nitrogen sources, metal nitride clusterfullerenes (NCFs) based on a variety of metals (Dy, Sc, Y, Gd, Lu, and mixed metals Sc/Dy, Sc/Gd, Sc/Lu, and Lu/Ce) have been synthesized based on a new "selective organic solid" (SOS) route. The synthesis of Dy-NCFs by using Dy/1 was studied in detail, and the optimum molar ratio of 1/Dy/C has been determined to be 2.5:1:10. For several representative metals such as Sc, Y, Gd, Dy, and Sc/Dy, we quantitatively compared the yield of M(3)N@C(80) synthesized by the SOS route with the reported "reactive gas atmosphere" route, thereby indicating that the yield of M(3)N@C(80) by using 1 could be comparable to that obtained by the reactive gas atmosphere route. Three other nitrogen sources (3-5) were also studied for comparison, which were mixed with Dy metal but did not result in the formation of Dy-NCF. A possible reaction scheme for the solid-state reaction of 1, metal, and graphite is proposed. The SOS route appears to be a general route for the synthesis of NCFs that promises both high selectivity of NCFs and high reproducibility of the fullerene yield. Another advantages of the SOS route compared to the reported "trimetallic nitride template" (TNT) process and the reactive gas atmosphere route is that no additional heating pretreatment is needed, thus simplifying the procedure and being much more facile.

Urea as a New and Cheap Nitrogen Source for the Synthesis of Metal Nitride Clusterfullerenes: The Role of Decomposed Products on the Selectivity of Fullerenes

“…[1,3,25] However, for the present method, metal oxide Sc 2 O 3 , COA C H T U N G T R E N N U N G (NH 2 ) 2 , and graphite are simply mixed and subjected to arc discharging directly without any additional heating pretreatment, thus the method is simplified and much more facile than the two commonly used methods. With such advantages, COA C H T U N G T R E N N U N G (NH 2 ) 2 as the new nitrogen source is expected to be established as a general route for NCFs based on other metals, studies into which are underway in our lab.…”

“…In addition, it has a similar bonding structure to guanidine and the nitrogen content of urea A C H T U N G T R E N N U N G (%47 wt %) is exactly the same as that in guanidinium thiocyanate, which has been used as the nitrogen source for the "selective organic solid" route. [25] Solid urea was mixed with Sc 2 O 3 and graphite powder with a certain molar ratio and subjected to direct current (DC) arc discharging (Scheme 1). [4,9,12,22,24,25] Therefore, clearly all of the reported Sc-based NCFs, Sc 3 ) is proportional to the HPLC peak intensity of fraction A, [27] the dependence of the yield of Sc 3 N@C 80 (I h + D 5h ) on the molar ratio of Sc 2 O 3 /COA C H T U N G T R E N N U N G (NH 2 ) 2 can be evaluated by the HPLC peak intensity of fraction A, which is plotted in Figure 3.…”

“…[25] Solid urea was mixed with Sc 2 O 3 and graphite powder with a certain molar ratio and subjected to direct current (DC) arc discharging (Scheme 1). [4,9,12,22,24,25] Therefore, clearly all of the reported Sc-based NCFs, Sc 3 ) is proportional to the HPLC peak intensity of fraction A, [27] the dependence of the yield of Sc 3 N@C 80 (I h + D 5h ) on the molar ratio of Sc 2 O 3 /COA C H T U N G T R E N N U N G (NH 2 ) 2 can be evaluated by the HPLC peak intensity of fraction A, which is plotted in Figure 3. Clearly the production of empty fullerenes (mainly C 60 and C 70 ) is always dominant under all of the conditions, while the yield of Sc 3 N@C 80 (I h + D 5h ) increases dramatically when as the nitrogen source is first compared with those obtained by using two different gaseous nitrogen sources, namely, N 2 and NH 3 , which are used in the TNT process and the reactive gas atmosphere route (see Figure 1 and Figure S2 in the Supporting Information), respectively.…”

“…[5] To overcome such a disadvantage, very recently we established the "selective organic solid" (SOS) route with guanidinium salts (guanidinium thiocyanate or guanidinium hydrochloride) as the organic solid nitrogen sources; this was a general route for the synthesis of NCFs with both high selectivity and high reproducibility of the yields of NCFs. [25,26] When considering that the synthetic methods for NCFs are limited to the four aforementioned routes and, in particular, that the solid nitrogen routes have been rarely studied, herein, we report the first use of urea (COA C H T U N G T R E N N U N G (NH 2 ) 2 ) as a new, cheap nitrogen source for the successful synthesis of Scbased NCFs. The optimum ratio of Sc 2 O 3 /COA C H T U N G T R E N N U N G (NH 2 ) 2 /C has been determined and the yield of Sc 3 N@C 80 (I h + D 5h ) per gram of Sc 2 O 3 by using COA C H T U N G T R E N N U N G (NH 2 ) 2 as the new nitrogen source was compared with that obtained by using other reAbstract: By using urea as the new nitrogen source, for the first time, Scbased metal nitride clusterfullerenes (NCFs), Sc 3 N@C 2n (2n = 80, 78, 70, 68), have been synthesized successfully.…”

“…[1d, 3,5,25] In the first attempt, Dunsch et al used calcium cyanamide, affording the generation of gaseous nitrogen for the TNT process, which resulted in the synthesis of Sc 3 N@C 80 NCF with a selectivity ranging from 3 to 42 %. [5] However, this "inorganic solid nitrogen" route was not widely applied because of low reproducibility of the fullerene yield.…”