[uogo]

hello all,
Hope this post goes here (eather here or analytical).
just wanting a little bit of help with Cu(II) complexes. i will try and explain this the best i can, if you have a Ln(III) metal with organic framework around it (unspecified for the time being).
Attached to that framework you have a 1,10-Phenanthroline (herein referred to as Phen) group.
now this complex will then be luminescent. if a Cu(II) (in the form of CuX₂) group was coordinated to the 2 Nitrogen's on the Phengroup the luminescence would be quenched. This is due to the Mechanism for the phen group being LMCT (ligand-to-metal charge transfer) and Cu(II) is quite effective a preventing LMCT.
Now if we do a direct substitution of the Phen group for a bipy (bpy) group my question is this: Would you still observe quenching.
for bipy dose not only support LMCT but also MLCT (metal to ligand charge transfer) i am aware that Cu(II) can in some circumstances also prevent MLCT. But I'm not certain here. you get MLCT from Cu(II) to bipy then LMCT from bipy to the Ln(III).
i know that not all Ln(III) would luminess but for this time i want to assume that the Ln would.
also if anybody could point me in the direction of some on line literature that goes into detail about how Cu(II) stops LMCT and some MLCT i would be grateful.
thank you for your time.

[dipesh747]

My first thought is that there would be no MLCT what so ever. I think this because the Nitrogen has a lone pair lying in its pi* orbital, and with a metal that has a 2+ oxidation state I don't see how MLCT would occur; surely there would only be lMCT. If there was any MLCT the only vacant orbital would be sigma*, and transfer into that orbital would be so unstable I don't think it would occur. I am no expert in this area so I may be wrong, but that was my first thought.

I also don't understand why you think phen would not pi back bond to the metal but bipy would? (I personally think both would), but in my opinion phen would have greater pi back bonding (through LMCT) as phen is in a large pi framework where as bipy is not.

[uogo]

It is purely the excited state i am interested in here. normally without the Cu(II) attached to the bipy hv (light) would excite electrons in bipy they would then travel via the triplit state to the Ln(III) excited state which would then cause the Ln(III) to luminess. when i say LMCT and MLCT i am referring to purely the excited state. As for the reason for my assumption of what ligand is MLCT, LMCT or both (with respect to excited state transfer causing luminescence) is a paper on the aforementioned."chemsoc rev 2009 metal-organic frameworks issue" if needed i can attach paper (if i figger out how). I could be compleatly wrong here i still have alot to learn.
thanks for the info.

[uogo]

ok sorry to spam another post again. i have been reading around still. and everything suggests that Cu(II) should still quench the luminescence of the lanthanum(III) ion.
Although i am not 100% certain.
most places state that this is for the most part due to "non-radiative deactivating process of the Cu(II) ion." now i would like to understand more about the process of this "deactivation".
a quick though would be the possibility of the Cu(II) ion "stealing" the energy that would normally go to the Ln(III) ion and then non-radiatively emit it so to speak.(a little crude i know).
i have and still am looking around for more information about it, and i would greatly appreciate any information on the subject or suggested reading.
thank you.