Table S3.

Normal mode assignments of the symmetrical COO⁻ stretching vibrations of model 2

S1			S2 (Mn1 oxidized)			S2 (Mn4 oxidized)
Frequency (cm−1)*	Intensity (km/mol)	Assignment	Frequency (cm−1)*	Intensity (km/mol)	Assignment	Frequency (cm−1)*	Intensity (km/mol)	Assignment
1,278	178	E189	1,264	413	E189	1,276	317	E189
1,284	87	A344	1,288	65	A344, E189	1,288	77	A344
1,305	212	E189	1,290	189	A344, E189	1,302	165	E189
1,325	80	D170	1,312	36	E333	1,304	85	E333
1,344	374	A344	1,327	43	D170	1,339	378	A344
1,351	93	D170	1,334	419	A344	1,360	123	D170
1,362	169	D342, E354, E189	1,346	64	E189	1,370	108	D342, E189
1,364	74	D61	1,351	53	D170	1,371	113	D61
1,367	168	E354, D342	1,352	239	D342, E333, E354	1,374	106	E354, E189
1,376	72	E189	1,354	61	E333, D342, E354, D170	1,375	85	E189, E354
1,376	121	E189, D342	1,358	221	E354, A344, D342	1,377	105	E189, D342
1,379	89	A344, E354	1,369	201	E189	1,379	61	A344
1,382	92	E354, A344, E189	1,372	120	D61	1,381	312	E333, D170
1,395	248	E333	1,379	83	A344, E354, E333	1,386	302	D170, E333, E354
1,400	45	A344	1,383	171	E333	1,389	133	E354, D170, E333, A344
1,406	130	D342	1,404	261	D170	1,412	236	D61
1,409	265	D170, D61	1,408	152	D342	1,421	237	D342
1,410	96	D61, D342	1,416	195	D61	1,428	44	E333
			1,422	54	E189
			1,433	46	E333, E354

^*Calculated frequencies were scaled with a factor of 0.9613 to adjust the frequency of a major peak of the calculated S₂/S₁ difference spectrum (an average spectrum of Mn₁- and Mn₄-oxidized S₂) to 1,401 cm⁻¹, where an intense negative band is located in the experimental spectrum.