The rather presumptious title assumes the laws and fundamental constants of physics are the same everywhere (they may not be). With this constraint (and without yet defining what is meant by strongest), consider the three molecules:
| Property
(CCSD/aug-cc-pVTZ) |
N≡N | (H-N≡N)+ | (H-N≡N-H)2+ |
|---|---|---|---|
| NN length, Å | 1.0967 | 1.0915 | 1.0795 |
| NN stretch, cm-1 | 2418.8 | 2356.4
2545.1a/2451.5b |
2226.3/3024.0
2688.4a/2567.7b |
| ELF NN basin
integration |
3.57 | 4.31 | 4.59 |
| QTAIM ρ(r)/∇2ρ(r) | 0.714/-3.38 | 0.690/-3.07 | 0.700/-2.96 |
| aValue for hydrogen mass of 10,000 bValue for hydrogen mass of 0.001. | |||
The series explores the effect of protonating dinitrogen (generally considered as strong as a diatomic bond gets).
So is the NN bond in HNNH2+ the strongest bond in the universe? Almost certainly. OK, so bonds with higher formal bond orders (Cr2 for example) exist, but they come nowhere near HN≡NH2+, which is crowned champion.
Oh, by the way, another article (DOI: 10.1063/1.1576756) claimed the title in 2003, but I make the claim for a stronger bond here!
In the mid to late 1990s as the Web developed, it was becoming more obvious…
I have written a few times about the so-called "anomeric effect", which relates to stereoelectronic…
The recent release of the DataCite Data Citation corpus, which has the stated aim of…
Following on from my template exploration of the Wilkinson hydrogenation catalyst, I now repeat this…
In the late 1980s, as I recollected here the equipment needed for real time molecular…
On 24th January 1984, the Macintosh computer was released, as all the media are informing…
View Comments
In the above post, I linked to an article claiming that the fine structure constant varies according to where in the universe it is measured. What I noticed about this article is that six blogs have already picked up on this, and all have commented in the form of trackbacks. It is an interesting second layer of peer review that perhaps we should adopt more of in chemistry?
I used a "trick" to purify the normal vibrational modes of the molecules. The trick was to make the mass of H so different from that of the N that the two modes do not mix. In the case above, the mass of H was made much larger than N. In fact, upon reflection, the correct answer is to make the mass of the H much lighter, not heavier. This means all N-H streching is factored out, since the ultra light H just rides on the N. The three wavenumbers become: 2418.8, 2451.5, 2567.7. The conclusion remains unchanged. I also note that this latter treatment is equivalent to the use of compliance constants, which was the method adopted in DOI: 10.1063/1.1576756
Henry,
What about O2 2+ dication? Is it a worthy contender? It is isoelectronic to nitrogen and its O-O bond of 1.073 Å had been claimed to be the shortest bond between two 2nd row atoms.
Dications are remarkable species. I had outlined "paradoxes and world records" associated with their electronic structure and reactivity in a 2003 Chem. Rev. paper (http://pubs.acs.org/doi/pdf/10.1021/cr0000628).
I did have a go earlier at O4; i.e. (-)O-O(+)=O(+)-O(-). The result is at 10042/20256 The central O-O length is 1.59Å.
At the same level as the calculations reported above (CCSD/aug-cc-pvtz) O2(2+) has a bond length of 1.0401Å and a vibrational wavenumber of 2337 cm-1. The handle for the calculation is 10042/20261. At the higher CCSD(T) level, the length is 1.050Å and the wavenumber 2185 cm-1 (10042/20262) I think this makes the bond shorter. Whether the force constant is is larger than the NN one in HNNH (2+) remains to be evaluated (the wavenumber is down, but the mass of the oxygen is up).
Just for fun, FO(3+), isoelectronic with O2(2+), comes out with a bond of 1.165Å and a wavenumber of 941 (CCSD(T)/aug-cc-pvtz)
And to complete this, NO(+) emerges as 1.069Å and 2356 cm-1 (CCSD(T)/aug-cc-pvtz).
Some baffled astronomer somewhere may be looking at a series of lines with a spacing of about 2451 cm-1 and wondering what they are. I say this because your hypothetical hydrogen of 0.001 amu is almost the mass of a positron! What is the stretching freq of N2-e+ ["proton" mass of 0.00054462 amu]? This molecule may be visible from here...